diff --git a/.travis.yml b/.travis.yml
index e27956f34e..0bc7c1ff0c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,8 +17,13 @@ branches:
   only:
   - master
   - develop
+  - release
+
 before_install:
-  - git clone -b develop --single-branch https://github.com/LearnLib/automatalib.git /tmp/automatalib-develop
+    # set Travis environment variables "AUTOMATALIB_FORK" and "AUTOMATALIB_BRANCH" to build custom AutomataLib versions.
+    # Defaults are "LearnLib" and the current/targeted LearnLib branch ($TRAVIS_BRANCH, relies on the same naming
+    # conventions between AutomataLib and LearnLib branches).
+  - git clone -b ${AUTOMATALIB_BRANCH:-$TRAVIS_BRANCH} --single-branch https://github.com/${AUTOMATALIB_FORK:-LearnLib}/automatalib.git /tmp/automatalib-develop
   - pushd /tmp/automatalib-develop
     # skip several aspects of the build process, because we are only interested in the compiled code
   - mvn install -DskipTests -Dmaven.javadoc.skip=true
diff --git a/README.md b/README.md
index 66a7118146..9ba64f2238 100644
--- a/README.md
+++ b/README.md
@@ -42,7 +42,8 @@ Note, that LearnLib requires Java 8.
 
 #### Building development versions
 
-If you intend to use development versions of LearnLib, simply clone the development branch of the repository
+If you intend to use development versions of LearnLib, you can either use the deployed SNAPSHOT artifacts from the continuous integration server (see [Using Development Versions](https://github.com/LearnLib/learnlib/wiki/Using-Development-Versions)), or build them yourself.
+Simply clone the development branch of the repository
 
 ```
 git clone -b develop --single-branch https://github.com/LearnLib/learnlib.git
diff --git a/algorithms/active/adt/pom.xml b/algorithms/active/adt/pom.xml
index 56f90a48b3..1020275603 100644
--- a/algorithms/active/adt/pom.xml
+++ b/algorithms/active/adt/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-algorithms-active-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/algorithms/active/adt/src/main/java/de/learnlib/algorithms/adt/learner/ADTLearner.java b/algorithms/active/adt/src/main/java/de/learnlib/algorithms/adt/learner/ADTLearner.java
index 402c2924a6..b13f2740cc 100644
--- a/algorithms/active/adt/src/main/java/de/learnlib/algorithms/adt/learner/ADTLearner.java
+++ b/algorithms/active/adt/src/main/java/de/learnlib/algorithms/adt/learner/ADTLearner.java
@@ -65,6 +65,7 @@
 import net.automatalib.words.Word;
 import net.automatalib.words.WordBuilder;
 import net.automatalib.words.impl.Alphabets;
+import net.automatalib.words.impl.SymbolHidingAlphabet;
 
 /**
  * The main learning algorithm.
@@ -101,7 +102,7 @@ public ADTLearner(final Alphabet<I> alphabet,
                       final ADTExtender adtExtender,
                       final SubtreeReplacer subtreeReplacer) {
 
-        this.alphabet = alphabet;
+        this.alphabet = SymbolHidingAlphabet.wrapIfMutable(alphabet);
         this.observationTree = new ObservationTree<>(this.alphabet);
         this.oracle = new SQOOTBridge<>(this.observationTree, oracle, true);
 
@@ -370,9 +371,17 @@ public void addAlphabetSymbol(I symbol) {
             return;
         }
 
-        this.alphabet = Alphabets.withNewSymbol(this.alphabet, symbol);
         this.hypothesis.addAlphabetSymbol(symbol);
-        this.observationTree.getObservationTree().addAlphabetSymbol(symbol);
+
+        SymbolHidingAlphabet.runWhileHiding(alphabet,
+                                            symbol,
+                                            () -> this.observationTree.getObservationTree().addAlphabetSymbol(symbol));
+
+        // since we share the alphabet instance with our hypothesis, our alphabet might have already been updated (if it
+        // was already a GrowableAlphabet)
+        if (!this.alphabet.containsSymbol(symbol)) {
+            this.alphabet = Alphabets.withNewSymbol(this.alphabet, symbol);
+        }
 
         for (final ADTState<I, O> s : this.hypothesis.getStates()) {
             this.openTransitions.add(this.hypothesis.createOpenTransition(s, symbol, this.adt.getRoot()));
diff --git a/algorithms/active/adt/src/main/java/de/learnlib/algorithms/adt/learner/ADTLearnerState.java b/algorithms/active/adt/src/main/java/de/learnlib/algorithms/adt/learner/ADTLearnerState.java
index d9b767cbc9..7441212109 100644
--- a/algorithms/active/adt/src/main/java/de/learnlib/algorithms/adt/learner/ADTLearnerState.java
+++ b/algorithms/active/adt/src/main/java/de/learnlib/algorithms/adt/learner/ADTLearnerState.java
@@ -37,7 +37,7 @@ public class ADTLearnerState<S, I, O> implements Serializable {
     private final ADTHypothesis<I, O> hypothesis;
     private final ADT<S, I, O> adt;
 
-    public ADTLearnerState(ADTHypothesis<I, O> hypothesis, ADT<S, I, O> adt) {
+    ADTLearnerState(ADTHypothesis<I, O> hypothesis, ADT<S, I, O> adt) {
         this.hypothesis = hypothesis;
         this.adt = adt;
     }
diff --git a/algorithms/active/dhc/pom.xml b/algorithms/active/dhc/pom.xml
index 70f2ef04c7..7211179719 100644
--- a/algorithms/active/dhc/pom.xml
+++ b/algorithms/active/dhc/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-algorithms-active-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/algorithms/active/dhc/src/main/java/de/learnlib/algorithms/dhc/mealy/MealyDHCState.java b/algorithms/active/dhc/src/main/java/de/learnlib/algorithms/dhc/mealy/MealyDHCState.java
index efeba844cd..2edbf1a718 100644
--- a/algorithms/active/dhc/src/main/java/de/learnlib/algorithms/dhc/mealy/MealyDHCState.java
+++ b/algorithms/active/dhc/src/main/java/de/learnlib/algorithms/dhc/mealy/MealyDHCState.java
@@ -34,7 +34,7 @@
  *
  * @author bainczyk
  */
-class MealyDHCState<I, O> implements Serializable {
+public class MealyDHCState<I, O> implements Serializable {
 
     private final LinkedHashSet<Word<I>> splitters;
     private final CompactMealy<I, O> hypothesis;
diff --git a/algorithms/active/discrimination-tree-vpda/pom.xml b/algorithms/active/discrimination-tree-vpda/pom.xml
index 135780f1d7..cbb42296a5 100644
--- a/algorithms/active/discrimination-tree-vpda/pom.xml
+++ b/algorithms/active/discrimination-tree-vpda/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-algorithms-active-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/algorithms/active/discrimination-tree/pom.xml b/algorithms/active/discrimination-tree/pom.xml
index 8d939bc5ad..874407f2d5 100644
--- a/algorithms/active/discrimination-tree/pom.xml
+++ b/algorithms/active/discrimination-tree/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-algorithms-active-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/algorithms/active/discrimination-tree/src/main/java/de/learnlib/algorithms/discriminationtree/AbstractDTLearner.java b/algorithms/active/discrimination-tree/src/main/java/de/learnlib/algorithms/discriminationtree/AbstractDTLearner.java
index cb34f0aab4..3a37bc0ceb 100644
--- a/algorithms/active/discrimination-tree/src/main/java/de/learnlib/algorithms/discriminationtree/AbstractDTLearner.java
+++ b/algorithms/active/discrimination-tree/src/main/java/de/learnlib/algorithms/discriminationtree/AbstractDTLearner.java
@@ -222,9 +222,14 @@ public void addAlphabetSymbol(I symbol) {
 
         final int newSymbolIdx = this.alphabet.size();
 
-        this.alphabet = Alphabets.withNewSymbol(this.alphabet, symbol);
         this.hypothesis.addAlphabetSymbol(symbol);
 
+        // since we share the alphabet instance with our hypothesis, our alphabet might have already been updated (if it
+        // was already a GrowableAlphabet)
+        if (!this.alphabet.containsSymbol(symbol)) {
+            this.alphabet = Alphabets.withNewSymbol(this.alphabet, symbol);
+        }
+
         for (final HState<I, D, SP, TP> s : this.hypothesis.getStates()) {
             final HTransition<I, D, SP, TP> newTrans = new HTransition<>(s, symbol, dtree.getRoot());
             s.setTransition(newSymbolIdx, newTrans);
diff --git a/algorithms/active/discrimination-tree/src/main/java/de/learnlib/algorithms/discriminationtree/hypothesis/DTLearnerHypothesis.java b/algorithms/active/discrimination-tree/src/main/java/de/learnlib/algorithms/discriminationtree/hypothesis/DTLearnerHypothesis.java
index 41c5d30357..d43ece67ee 100644
--- a/algorithms/active/discrimination-tree/src/main/java/de/learnlib/algorithms/discriminationtree/hypothesis/DTLearnerHypothesis.java
+++ b/algorithms/active/discrimination-tree/src/main/java/de/learnlib/algorithms/discriminationtree/hypothesis/DTLearnerHypothesis.java
@@ -31,7 +31,6 @@
 import net.automatalib.visualization.DefaultVisualizationHelper;
 import net.automatalib.visualization.VisualizationHelper;
 import net.automatalib.words.Alphabet;
-import net.automatalib.words.GrowingAlphabet;
 import net.automatalib.words.Word;
 import net.automatalib.words.impl.Alphabets;
 
@@ -132,8 +131,8 @@ public HState<I, O, SP, TP> getSuccessor(HTransition<I, O, SP, TP> trans) {
     @Override
     public void addAlphabetSymbol(I symbol) {
 
-        if (this.alphabet instanceof GrowingAlphabet) {
-            ((GrowingAlphabet<I>) this.alphabet).addSymbol(symbol);
+        if (this.alphabet.containsSymbol(symbol)) {
+            return;
         }
 
         this.alphabet = Alphabets.withNewSymbol(this.alphabet, symbol);
diff --git a/algorithms/active/kearns-vazirani/pom.xml b/algorithms/active/kearns-vazirani/pom.xml
index 0f26aa2513..5a2b08875c 100644
--- a/algorithms/active/kearns-vazirani/pom.xml
+++ b/algorithms/active/kearns-vazirani/pom.xml
@@ -20,7 +20,7 @@ limitations under the License.
     <parent>
         <groupId>de.learnlib</groupId>
         <artifactId>learnlib-algorithms-active-parent</artifactId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
     <artifactId>learnlib-kearns-vazirani</artifactId>
diff --git a/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/dfa/KearnsVaziraniDFA.java b/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/dfa/KearnsVaziraniDFA.java
index fc9caad445..fcb51cf787 100644
--- a/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/dfa/KearnsVaziraniDFA.java
+++ b/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/dfa/KearnsVaziraniDFA.java
@@ -267,9 +267,14 @@ public void addAlphabetSymbol(I symbol) {
         }
 
         final int inputIdx = this.alphabet.size();
-        this.alphabet = Alphabets.withNewSymbol(this.alphabet, symbol);
         this.hypothesis.addAlphabetSymbol(symbol);
 
+        // since we share the alphabet instance with our hypothesis, our alphabet might have already been updated (if it
+        // was already a GrowableAlphabet)
+        if (!this.alphabet.containsSymbol(symbol)) {
+            this.alphabet = Alphabets.withNewSymbol(this.alphabet, symbol);
+        }
+
         // use new list to prevent concurrent modification exception
         for (final StateInfo<I, Boolean> si : new ArrayList<>(this.stateInfos)) {
             final int state = si.id;
diff --git a/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/dfa/KearnsVaziraniDFAState.java b/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/dfa/KearnsVaziraniDFAState.java
index 421310b9fa..5ec0a18220 100644
--- a/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/dfa/KearnsVaziraniDFAState.java
+++ b/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/dfa/KearnsVaziraniDFAState.java
@@ -30,7 +30,7 @@
  *
  * @author bainczyk
  */
-class KearnsVaziraniDFAState<I> implements Serializable {
+public class KearnsVaziraniDFAState<I> implements Serializable {
 
     private final CompactDFA<I> hypothesis;
     private final BinaryDTree<I, StateInfo<I, Boolean>> discriminationTree;
diff --git a/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/mealy/KearnsVaziraniMealy.java b/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/mealy/KearnsVaziraniMealy.java
index a1a36620e8..74e0902b43 100644
--- a/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/mealy/KearnsVaziraniMealy.java
+++ b/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/mealy/KearnsVaziraniMealy.java
@@ -283,9 +283,14 @@ public void addAlphabetSymbol(I symbol) {
         }
 
         final int inputIdx = this.alphabet.size();
-        this.alphabet = Alphabets.withNewSymbol(this.alphabet, symbol);
         this.hypothesis.addAlphabetSymbol(symbol);
 
+        // since we share the alphabet instance with our hypothesis, our alphabet might have already been updated (if it
+        // was already a GrowableAlphabet)
+        if (!this.alphabet.containsSymbol(symbol)) {
+            this.alphabet = Alphabets.withNewSymbol(this.alphabet, symbol);
+        }
+
         // use new list to prevent concurrent modification exception
         for (final StateInfo<I, Word<O>> si : new ArrayList<>(this.stateInfos)) {
             final int state = si.id;
diff --git a/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/mealy/KearnsVaziraniMealyState.java b/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/mealy/KearnsVaziraniMealyState.java
index eba16b9840..8b59a4cc01 100644
--- a/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/mealy/KearnsVaziraniMealyState.java
+++ b/algorithms/active/kearns-vazirani/src/main/java/de/learnlib/algorithms/kv/mealy/KearnsVaziraniMealyState.java
@@ -33,7 +33,7 @@
  *
  * @author bainczyk
  */
-class KearnsVaziraniMealyState<I, O> implements Serializable {
+public class KearnsVaziraniMealyState<I, O> implements Serializable {
 
     private final CompactMealy<I, O> hypothesis;
     private final AbstractWordBasedDiscriminationTree<I, Word<O>, StateInfo<I, Word<O>>> discriminationTree;
diff --git a/algorithms/active/lstar/pom.xml b/algorithms/active/lstar/pom.xml
index 4565d2b968..ab86d1644b 100644
--- a/algorithms/active/lstar/pom.xml
+++ b/algorithms/active/lstar/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-algorithms-active-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AbstractAutomatonLStar.java b/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AbstractAutomatonLStar.java
index ed65ffbb04..d68b6043fb 100644
--- a/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AbstractAutomatonLStar.java
+++ b/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AbstractAutomatonLStar.java
@@ -28,6 +28,7 @@
 import net.automatalib.automata.MutableDeterministic;
 import net.automatalib.commons.util.collections.CollectionsUtil;
 import net.automatalib.words.Alphabet;
+import net.automatalib.words.impl.SymbolHidingAlphabet;
 
 /**
  * Abstract base class for algorithms that produce (subclasses of) {@link MutableDeterministic} automata.
@@ -63,7 +64,7 @@ public abstract class AbstractAutomatonLStar<A, I, D, S, T, SP, TP, AI extends M
      *         the learning oracle
      */
     protected AbstractAutomatonLStar(Alphabet<I> alphabet, MembershipOracle<I, D> oracle, AI internalHyp) {
-        super(alphabet, oracle);
+        super(SymbolHidingAlphabet.wrapIfMutable(alphabet), oracle);
         this.internalHyp = internalHyp;
         internalHyp.clear();
     }
@@ -191,8 +192,10 @@ public void addAlphabetSymbol(I symbol) {
             return;
         }
 
-        super.addAlphabetSymbol(symbol);
         this.internalHyp.addAlphabetSymbol(symbol);
+
+        SymbolHidingAlphabet.runWhileHiding(alphabet, symbol, () -> super.addAlphabetSymbol(symbol));
+
         this.updateInternalHypothesis();
     }
 
diff --git a/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AbstractLStar.java b/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AbstractLStar.java
index 1e9493cb0b..0af041d97b 100644
--- a/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AbstractLStar.java
+++ b/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AbstractLStar.java
@@ -232,10 +232,14 @@ public void addAlphabetSymbol(I symbol) {
             return;
         }
 
-        this.alphabet = Alphabets.withNewSymbol(this.alphabet, symbol);
-
         final List<List<Row<I>>> unclosed = this.table.addAlphabetSymbol(symbol, oracle);
 
+        // since we share the alphabet instance with our observation table, our alphabet might have already been updated
+        // (if it was already a GrowableAlphabet)
+        if (!this.alphabet.containsSymbol(symbol)) {
+            this.alphabet = Alphabets.withNewSymbol(this.alphabet, symbol);
+        }
+
         completeConsistentTable(unclosed, true);
     }
 }
diff --git a/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AbstractLStarState.java b/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AbstractLStarState.java
index 4f268fe65e..7a6b9418af 100644
--- a/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AbstractLStarState.java
+++ b/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AbstractLStarState.java
@@ -33,7 +33,7 @@ public abstract class AbstractLStarState<I, D> implements Serializable {
 
     private final GenericObservationTable<I, D> observationTable;
 
-    public AbstractLStarState(final GenericObservationTable<I, D> observationTable) {
+    AbstractLStarState(final GenericObservationTable<I, D> observationTable) {
         this.observationTable = observationTable;
     }
 
diff --git a/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AutomatonLStarState.java b/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AutomatonLStarState.java
index d63a678ade..8ad48478dd 100644
--- a/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AutomatonLStarState.java
+++ b/algorithms/active/lstar/src/main/java/de/learnlib/algorithms/lstar/AutomatonLStarState.java
@@ -40,9 +40,9 @@ public class AutomatonLStarState<I, D, AI, S> extends AbstractLStarState<I, D> {
     private final AI hypothesis;
     private final List<StateInfo<S, I>> stateInfos;
 
-    public AutomatonLStarState(final GenericObservationTable<I, D> observationTable,
-                               final AI hypothesis,
-                               final List<StateInfo<S, I>> stateInfos) {
+    AutomatonLStarState(final GenericObservationTable<I, D> observationTable,
+                        final AI hypothesis,
+                        final List<StateInfo<S, I>> stateInfos) {
         super(observationTable);
         this.hypothesis = hypothesis;
         this.stateInfos = stateInfos;
diff --git a/algorithms/active/nlstar/pom.xml b/algorithms/active/nlstar/pom.xml
index 34529a8574..124978483b 100644
--- a/algorithms/active/nlstar/pom.xml
+++ b/algorithms/active/nlstar/pom.xml
@@ -20,7 +20,7 @@ limitations under the License.
     <parent>
         <groupId>de.learnlib</groupId>
         <artifactId>learnlib-algorithms-active-parent</artifactId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
     </parent>
     <name>LearnLib :: Algorithms :: NL*</name>
     <artifactId>learnlib-nlstar</artifactId>
diff --git a/algorithms/active/pom.xml b/algorithms/active/pom.xml
index c2da98e796..a9653ce25b 100644
--- a/algorithms/active/pom.xml
+++ b/algorithms/active/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-algorithms-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/algorithms/active/ttt-vpda/pom.xml b/algorithms/active/ttt-vpda/pom.xml
index 48e22d71cd..cf2daf847c 100644
--- a/algorithms/active/ttt-vpda/pom.xml
+++ b/algorithms/active/ttt-vpda/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-algorithms-active-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/algorithms/active/ttt/pom.xml b/algorithms/active/ttt/pom.xml
index 1424df3706..71d3e2e498 100644
--- a/algorithms/active/ttt/pom.xml
+++ b/algorithms/active/ttt/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-algorithms-active-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/algorithms/active/ttt/src/main/java/de/learnlib/algorithms/ttt/base/AbstractTTTLearner.java b/algorithms/active/ttt/src/main/java/de/learnlib/algorithms/ttt/base/AbstractTTTLearner.java
index 880ca1f894..e265e09a38 100644
--- a/algorithms/active/ttt/src/main/java/de/learnlib/algorithms/ttt/base/AbstractTTTLearner.java
+++ b/algorithms/active/ttt/src/main/java/de/learnlib/algorithms/ttt/base/AbstractTTTLearner.java
@@ -949,9 +949,14 @@ public void addAlphabetSymbol(I symbol) {
 
         final int newSymbolIdx = this.alphabet.size();
 
-        this.alphabet = Alphabets.withNewSymbol(this.alphabet, symbol);
         this.hypothesis.addAlphabetSymbol(symbol);
 
+        // since we share the alphabet instance with our hypothesis, our alphabet might have already been updated (if it
+        // was already a GrowableAlphabet)
+        if (!this.alphabet.containsSymbol(symbol)) {
+            this.alphabet = Alphabets.withNewSymbol(this.alphabet, symbol);
+        }
+
         for (final TTTState<I, D> s : this.hypothesis.getStates()) {
             final TTTTransition<I, D> trans = createTransition(s, symbol);
             trans.setNonTreeTarget(dtree.getRoot());
diff --git a/algorithms/passive/pom.xml b/algorithms/passive/pom.xml
index 2e97a5d75f..47f483a8d7 100644
--- a/algorithms/passive/pom.xml
+++ b/algorithms/passive/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-algorithms-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/algorithms/passive/rpni-edsm/pom.xml b/algorithms/passive/rpni-edsm/pom.xml
index a9560d3a75..c81b986d6e 100644
--- a/algorithms/passive/rpni-edsm/pom.xml
+++ b/algorithms/passive/rpni-edsm/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-algorithms-passive-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/algorithms/passive/rpni-mdl/pom.xml b/algorithms/passive/rpni-mdl/pom.xml
index 773b2478ce..755a51262e 100644
--- a/algorithms/passive/rpni-mdl/pom.xml
+++ b/algorithms/passive/rpni-mdl/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-algorithms-passive-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/algorithms/passive/rpni/pom.xml b/algorithms/passive/rpni/pom.xml
index 2abc6bc323..2068feca23 100644
--- a/algorithms/passive/rpni/pom.xml
+++ b/algorithms/passive/rpni/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-algorithms-passive-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/algorithms/pom.xml b/algorithms/pom.xml
index bf16efa7d0..686a169ccf 100644
--- a/algorithms/pom.xml
+++ b/algorithms/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-build-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../build-parent/pom.xml</relativePath>
     </parent>
 
diff --git a/api/pom.xml b/api/pom.xml
index b0e48c9ff4..ebf60c1e05 100644
--- a/api/pom.xml
+++ b/api/pom.xml
@@ -21,7 +21,7 @@ limitations under the License.
     <parent>
         <groupId>de.learnlib</groupId>
         <artifactId>learnlib-build-parent</artifactId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../build-parent/pom.xml</relativePath>
     </parent>
 
diff --git a/archetypes/basic/pom.xml b/archetypes/basic/pom.xml
index 827dc6f61a..cd4c43efad 100644
--- a/archetypes/basic/pom.xml
+++ b/archetypes/basic/pom.xml
@@ -27,7 +27,7 @@ limitations under the License.
     <parent>
         <groupId>de.learnlib.archetypes</groupId>
         <artifactId>learnlib-archetypes-parent</artifactId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/archetypes/complete/pom.xml b/archetypes/complete/pom.xml
index a7b496adbd..cbed117de2 100644
--- a/archetypes/complete/pom.xml
+++ b/archetypes/complete/pom.xml
@@ -27,7 +27,7 @@ limitations under the License.
     <parent>
         <groupId>de.learnlib.archetypes</groupId>
         <artifactId>learnlib-archetypes-parent</artifactId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/archetypes/pom.xml b/archetypes/pom.xml
index 72d09bc1b2..3d64afea06 100644
--- a/archetypes/pom.xml
+++ b/archetypes/pom.xml
@@ -28,7 +28,7 @@ limitations under the License.
     <parent>
         <groupId>de.learnlib</groupId>
         <artifactId>learnlib-build-parent</artifactId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../build-parent/pom.xml</relativePath>
     </parent>
 
diff --git a/build-parent/pom.xml b/build-parent/pom.xml
index dd786bd0b3..b496ab0083 100644
--- a/build-parent/pom.xml
+++ b/build-parent/pom.xml
@@ -30,7 +30,7 @@ limitations under the License.
     <parent>
         <groupId>de.learnlib</groupId>
         <artifactId>learnlib-parent</artifactId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/build-tools/pom.xml b/build-tools/pom.xml
index 5256056f13..13a407b42a 100644
--- a/build-tools/pom.xml
+++ b/build-tools/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/commons/acex/pom.xml b/commons/acex/pom.xml
index 21da6a13f1..dfd80e677f 100644
--- a/commons/acex/pom.xml
+++ b/commons/acex/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-commons-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/commons/counterexamples/pom.xml b/commons/counterexamples/pom.xml
index 4ec4cb94f4..7f7201fd5b 100644
--- a/commons/counterexamples/pom.xml
+++ b/commons/counterexamples/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-commons-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/commons/pom.xml b/commons/pom.xml
index 3a192c565f..19a7ae9788 100644
--- a/commons/pom.xml
+++ b/commons/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-build-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../build-parent/pom.xml</relativePath>
     </parent>
 
diff --git a/commons/settings/pom.xml b/commons/settings/pom.xml
index d4a30adfe2..9d50ceb028 100644
--- a/commons/settings/pom.xml
+++ b/commons/settings/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-commons-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/commons/util/pom.xml b/commons/util/pom.xml
index a559a61e74..4dcef41ff5 100644
--- a/commons/util/pom.xml
+++ b/commons/util/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-commons-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/commons/util/src/main/java/de/learnlib/util/statistics/SimpleProfiler.java b/commons/util/src/main/java/de/learnlib/util/statistics/SimpleProfiler.java
index f923235981..1b914671d6 100644
--- a/commons/util/src/main/java/de/learnlib/util/statistics/SimpleProfiler.java
+++ b/commons/util/src/main/java/de/learnlib/util/statistics/SimpleProfiler.java
@@ -13,7 +13,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
 package de.learnlib.util.statistics;
 
 import java.util.Map;
@@ -34,7 +33,6 @@ public final class SimpleProfiler {
 
     private static final Map<String, Counter> CUMULATED = new ConcurrentHashMap<>();
     private static final Map<String, Long> PENDING = new ConcurrentHashMap<>();
-    private static final boolean PROFILE = true;
     private static final LearnLogger LOGGER = LearnLogger.getLogger(SimpleProfiler.class.getName());
     private static final double MILLISECONDS_PER_SECOND = 1000.0;
 
@@ -43,7 +41,7 @@ private SimpleProfiler() {
     }
 
     /**
-     * reset internal data.
+     * Reset internal data.
      */
     public static void reset() {
         CUMULATED.clear();
@@ -51,40 +49,46 @@ public static void reset() {
     }
 
     /**
-     * start activity.
+     * Start the timer identified by the given key.
+     *
+     * @param name
+     *         The name of the timer to be started.
      */
     public static void start(String name) {
-        if (!PROFILE) {
-            return;
-        }
-        long start = System.currentTimeMillis();
-
-        PENDING.put(name, start);
-
+        PENDING.put(name, System.currentTimeMillis());
     }
 
     /**
-     * stop activity.
+     * Stop the timer identified by the given key. After stopping a timer, the time passed from its
+     * {@link #start(String) initialization} will be added to the cumulated time of the specific timer.
+     *
+     * @param name
+     *         The name of the timer to be stopped.
      */
     public static void stop(String name) {
-        if (!PROFILE) {
-            return;
-        }
         Long start = PENDING.remove(name);
         if (start == null) {
             return;
         }
         long duration = System.currentTimeMillis() - start;
-        Counter sum = CUMULATED.get(name);
-        if (sum == null) {
-            sum = new Counter(name, "ms");
-        }
+        Counter sum = CUMULATED.computeIfAbsent(name, k -> new Counter(k, "ms"));
         sum.increment(duration);
-        CUMULATED.put(name, sum);
     }
 
     /**
-     * get profiling results as string.
+     * Return the counter for the cumulated (passed) time of the given timer.
+     *
+     * @param name
+     *         The name of the timer to be returned.
+     *
+     * @return The counter for tracking the passed milliseconds of the timer
+     */
+    public static Counter cumulated(String name) {
+        return CUMULATED.get(name);
+    }
+
+    /**
+     * Get profiling results as string.
      */
     @Nonnull
     public static String getResults() {
@@ -100,7 +104,7 @@ public static String getResults() {
     }
 
     /**
-     * log results in category PROFILING.
+     * Log results in category PROFILING.
      */
     public static void logResults() {
         for (Entry<String, Counter> e : CUMULATED.entrySet()) {
diff --git a/datastructures/discrimination-tree/pom.xml b/datastructures/discrimination-tree/pom.xml
index a34b9efb7a..e6297ad84b 100644
--- a/datastructures/discrimination-tree/pom.xml
+++ b/datastructures/discrimination-tree/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-datastructures-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/datastructures/list/pom.xml b/datastructures/list/pom.xml
index 7181a311ea..dabdccf9c2 100644
--- a/datastructures/list/pom.xml
+++ b/datastructures/list/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-datastructures-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/datastructures/observation-table/pom.xml b/datastructures/observation-table/pom.xml
index 9cbd390944..1ed5fcd8dd 100644
--- a/datastructures/observation-table/pom.xml
+++ b/datastructures/observation-table/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-datastructures-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/datastructures/pom.xml b/datastructures/pom.xml
index ce4b9cc9fe..39a6c92c97 100644
--- a/datastructures/pom.xml
+++ b/datastructures/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-build-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../build-parent/pom.xml</relativePath>
     </parent>
 
diff --git a/datastructures/pta/pom.xml b/datastructures/pta/pom.xml
index 352a3e2fad..a55afa3ff8 100644
--- a/datastructures/pta/pom.xml
+++ b/datastructures/pta/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-datastructures-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/distribution/pom.xml b/distribution/pom.xml
index 6e514826d7..efd3dfb1a3 100644
--- a/distribution/pom.xml
+++ b/distribution/pom.xml
@@ -20,7 +20,7 @@ limitations under the License.
     <parent>
         <groupId>de.learnlib</groupId>
         <artifactId>learnlib-build-parent</artifactId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../build-parent/pom.xml</relativePath>
     </parent>
 
@@ -29,6 +29,13 @@ limitations under the License.
     <packaging>pom</packaging>
     <name>LearnLib :: Distribution</name>
 
+    <description>
+        An artifact that aggregates all other artifacts of LearnLib to produce an Uber-JAR that can be used in
+        non-maven environments. Likewise, this single artifact may be used in maven-aware environments to declare a
+        dependency on all LearnLib artifacts.
+    </description>
+
+
     <!--
     All packaged AutomataLib dependencies.
 
diff --git a/drivers/basic/pom.xml b/drivers/basic/pom.xml
index 416345f7c1..374fef6b8a 100644
--- a/drivers/basic/pom.xml
+++ b/drivers/basic/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-drivers-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/drivers/mapper/pom.xml b/drivers/mapper/pom.xml
index 7150407cf1..1f22d446f9 100644
--- a/drivers/mapper/pom.xml
+++ b/drivers/mapper/pom.xml
@@ -20,7 +20,7 @@ limitations under the License.
     <parent>
         <groupId>de.learnlib</groupId>
         <artifactId>learnlib-drivers-parent</artifactId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/drivers/pom.xml b/drivers/pom.xml
index d809aed7d4..bf4bc7d9e9 100644
--- a/drivers/pom.xml
+++ b/drivers/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-build-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../build-parent/pom.xml</relativePath>
     </parent>
 
diff --git a/drivers/simulator/pom.xml b/drivers/simulator/pom.xml
index e0ff211adb..c3a70769e0 100644
--- a/drivers/simulator/pom.xml
+++ b/drivers/simulator/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-drivers-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/examples/pom.xml b/examples/pom.xml
index bf65310064..e64a8bc930 100644
--- a/examples/pom.xml
+++ b/examples/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-build-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../build-parent/pom.xml</relativePath>
     </parent>
 
diff --git a/oracles/equivalence-oracles/pom.xml b/oracles/equivalence-oracles/pom.xml
index e4062ba505..b2dffeb6f3 100644
--- a/oracles/equivalence-oracles/pom.xml
+++ b/oracles/equivalence-oracles/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-oracles-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/oracles/filters/cache/pom.xml b/oracles/filters/cache/pom.xml
index 5fc95876b1..a993738db4 100644
--- a/oracles/filters/cache/pom.xml
+++ b/oracles/filters/cache/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-filters-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/oracles/filters/cache/src/main/java/de/learnlib/filter/cache/mealy/MealyCacheOracle.java b/oracles/filters/cache/src/main/java/de/learnlib/filter/cache/mealy/MealyCacheOracle.java
index 26b05d5027..ad791eadee 100644
--- a/oracles/filters/cache/src/main/java/de/learnlib/filter/cache/mealy/MealyCacheOracle.java
+++ b/oracles/filters/cache/src/main/java/de/learnlib/filter/cache/mealy/MealyCacheOracle.java
@@ -214,9 +214,15 @@ private MasterQuery<I, O> createMasterQuery(Word<I> word) {
         if (errorSyms == null) {
             return new MasterQuery<>(word);
         }
+
         int wbSize = wb.size();
+
+        if (wbSize == 0) {
+            return new MasterQuery<>(word, errorSyms);
+        }
+
         O repSym = errorSyms.get(wb.getSymbol(wbSize - 1));
-        if (wbSize == 0 || repSym == null) {
+        if (repSym == null) {
             return new MasterQuery<>(word, errorSyms);
         }
 
diff --git a/oracles/filters/pom.xml b/oracles/filters/pom.xml
index 8bc053527e..4f1a586db0 100644
--- a/oracles/filters/pom.xml
+++ b/oracles/filters/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-oracles-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/oracles/filters/reuse/pom.xml b/oracles/filters/reuse/pom.xml
index 343638ed25..7a74fd692d 100644
--- a/oracles/filters/reuse/pom.xml
+++ b/oracles/filters/reuse/pom.xml
@@ -19,7 +19,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-filters-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/oracles/filters/statistics/pom.xml b/oracles/filters/statistics/pom.xml
index f06d22b31a..2c0a90cd07 100644
--- a/oracles/filters/statistics/pom.xml
+++ b/oracles/filters/statistics/pom.xml
@@ -19,7 +19,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-filters-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/oracles/membership-oracles/pom.xml b/oracles/membership-oracles/pom.xml
index a85be42305..ecd694090f 100644
--- a/oracles/membership-oracles/pom.xml
+++ b/oracles/membership-oracles/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-oracles-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/oracles/parallelism/pom.xml b/oracles/parallelism/pom.xml
index 4c90367f84..91698999c1 100644
--- a/oracles/parallelism/pom.xml
+++ b/oracles/parallelism/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-oracles-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/oracles/pom.xml b/oracles/pom.xml
index d6e10de6c4..8fa0d6a20c 100644
--- a/oracles/pom.xml
+++ b/oracles/pom.xml
@@ -22,7 +22,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-build-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../build-parent/pom.xml</relativePath>
     </parent>
 
diff --git a/pom.xml b/pom.xml
index 75da7592f7..53c914e0da 100644
--- a/pom.xml
+++ b/pom.xml
@@ -24,7 +24,7 @@ limitations under the License.
     -->
     <groupId>de.learnlib</groupId>
     <artifactId>learnlib-parent</artifactId>
-    <version>0.13.0</version>
+    <version>0.13.1</version>
     <packaging>pom</packaging>
     <name>LearnLib</name>
     <url>http://learnlib.github.io/learnlib/maven-site/${project.version}</url>
@@ -129,7 +129,7 @@ limitations under the License.
         <connection>scm:git:git@github.com:LearnLib/learnlib.git</connection>
         <developerConnection>scm:git:git@github.com:LearnLib/learnlib.git</developerConnection>
         <url>https://github.com/LearnLib/learnlib/tree/develop</url>
-        <tag>learnlib-0.13.0</tag>
+        <tag>learnlib-0.13.1</tag>
     </scm>
 
     <!--
@@ -187,7 +187,7 @@ limitations under the License.
         <upload-plugin.version>1.1</upload-plugin.version>
 
         <!-- dependency versions -->
-        <automatalib.version>0.7.0</automatalib.version>
+        <automatalib.version>0.7.1</automatalib.version>
         <buildergen.version>0.1</buildergen.version>
         <checkstyle.version>8.1</checkstyle.version>
         <findbugs-annotations.version>3.0.2</findbugs-annotations.version>
@@ -410,14 +410,6 @@ limitations under the License.
                 </executions>
             </plugin>
         </plugins>
-
-        <extensions>
-            <extension>
-                <groupId>org.apache.maven.wagon</groupId>
-                <artifactId>wagon-ssh</artifactId>
-                <version>2.6</version>
-            </extension>
-        </extensions>
     </build>
 
     <!--
diff --git a/test-support/learner-it-support/pom.xml b/test-support/learner-it-support/pom.xml
index 2f9f3a5c31..56a8af2bb1 100644
--- a/test-support/learner-it-support/pom.xml
+++ b/test-support/learner-it-support/pom.xml
@@ -21,7 +21,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-test-support-parent</artifactId>
         <groupId>de.learnlib.testsupport</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/test-support/learner-it-support/src/main/java/de/learnlib/testsupport/AbstractGrowingAlphabetTest.java b/test-support/learner-it-support/src/main/java/de/learnlib/testsupport/AbstractGrowingAlphabetTest.java
index 854597cbb9..00f1c6bc60 100644
--- a/test-support/learner-it-support/src/main/java/de/learnlib/testsupport/AbstractGrowingAlphabetTest.java
+++ b/test-support/learner-it-support/src/main/java/de/learnlib/testsupport/AbstractGrowingAlphabetTest.java
@@ -18,7 +18,6 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
-import java.util.Random;
 
 import de.learnlib.api.algorithm.LearningAlgorithm;
 import de.learnlib.api.algorithm.feature.SupportsGrowingAlphabet;
@@ -28,7 +27,6 @@
 import net.automatalib.util.automata.Automata;
 import net.automatalib.words.Alphabet;
 import net.automatalib.words.Word;
-import net.automatalib.words.WordBuilder;
 import net.automatalib.words.impl.Alphabets;
 import net.automatalib.words.impl.SimpleAlphabet;
 import org.testng.Assert;
@@ -43,15 +41,12 @@
  */
 public abstract class AbstractGrowingAlphabetTest<L extends SupportsGrowingAlphabet<I> & LearningAlgorithm<M, I, D>, M extends UniversalDeterministicAutomaton<?, I, ?, ?, ?> & Output<I, D>, OR, I, D> {
 
-    private static final int MAX_VERIFICATION_TRIES = 100;
     protected static final int RANDOM_SEED = 42;
     protected static final int DEFAULT_AUTOMATON_SIZE = 15;
 
-    private Random random;
-
     private M target;
 
-    private L learner;
+    private OR oracle;
 
     private Alphabet<I> initialAlphabet;
 
@@ -59,8 +54,6 @@ public abstract class AbstractGrowingAlphabetTest<L extends SupportsGrowingAlpha
 
     @BeforeClass
     public void setup() {
-        random = new Random(RANDOM_SEED);
-
         initialAlphabet = getInitialAlphabet();
         alphabetExtensions = getAlphabetExtensions();
 
@@ -69,9 +62,7 @@ public void setup() {
         compoundAlphabet.addAll(alphabetExtensions);
 
         target = getTarget(Alphabets.fromList(compoundAlphabet));
-        final OR oracle = getOracle(target);
-
-        learner = getLearner(oracle, initialAlphabet);
+        oracle = getOracle(target);
     }
 
     protected abstract Alphabet<I> getInitialAlphabet();
@@ -86,11 +77,41 @@ public void setup() {
 
     @Test
     public void testInitialAlphabet() {
+        testAlphabet(initialAlphabet);
+    }
+
+    /**
+     * In case of passing a growing alphabet, the learners may use the existing
+     * {@link net.automatalib.words.GrowingAlphabet#addSymbol(Object)} functionality. Due to references, this may alter
+     * their behavior. Check it!
+     */
+    @Test
+    public void testGrowingAlphabetAlphabet() {
+        testAlphabet(new SimpleAlphabet<>(initialAlphabet));
+    }
+
+    private void testAlphabet(Alphabet<I> alphabet) {
+        final L learner = getLearner(oracle, alphabet);
+
         learner.startLearning();
-        this.performLearnLoop(initialAlphabet);
+        this.performLearnLoopAndCheck(learner, alphabet);
+
+        final List<I> currentAlphabet = new ArrayList<>(alphabet.size() + alphabetExtensions.size());
+        currentAlphabet.addAll(alphabet);
+
+        for (final I i : alphabetExtensions) {
+            currentAlphabet.add(i);
+            learner.addAlphabetSymbol(i);
+
+            final UniversalDeterministicAutomaton<?, I, ?, ?, ?> hyp = learner.getHypothesisModel();
+
+            this.checkCompletenessOfHypothesis(hyp, currentAlphabet);
+            this.performLearnLoopAndCheck(learner, currentAlphabet);
+        }
+
     }
 
-    private void performLearnLoop(final Alphabet<I> effectiveAlphabet) {
+    private void performLearnLoopAndCheck(final L learner, final Collection<? extends I> effectiveAlphabet) {
 
         M hyp = learner.getHypothesisModel();
         Word<I> sepWord = Automata.findSeparatingWord(target, hyp, effectiveAlphabet);
@@ -108,33 +129,14 @@ private void performLearnLoop(final Alphabet<I> effectiveAlphabet) {
         Assert.assertTrue(Automata.testEquivalence(target, hyp, effectiveAlphabet));
     }
 
-    @Test(dependsOnMethods = "testInitialAlphabet")
-    public void testAddingAlphabetSymbols() {
-        final Alphabet<I> currentAlphabet = new SimpleAlphabet<>(initialAlphabet);
-
-        for (final I i : alphabetExtensions) {
-            currentAlphabet.add(i);
-            learner.addAlphabetSymbol(i);
-
-            this.checkCompletenessOfHypothesis(currentAlphabet);
-            this.performLearnLoop(currentAlphabet);
-        }
-    }
-
-    private void checkCompletenessOfHypothesis(final Alphabet<I> alphabet) {
+    private <S, T> void checkCompletenessOfHypothesis(final UniversalDeterministicAutomaton<S, I, T, ?, ?> hypothesis, final Collection<? extends I> alphabet) {
+        for (final S s : hypothesis.getStates()) {
+            for (final I i : alphabet) {
+                final T trans = hypothesis.getTransition(s, i);
 
-        final int alphabetSize = alphabet.size();
-        final M hypothesis = learner.getHypothesisModel();
-
-        for (int i = 0; i < MAX_VERIFICATION_TRIES; i++) {
-            final WordBuilder<I> testTraceBuilder = new WordBuilder<>(i);
-
-            for (int j = 0; j < i; j++) {
-                testTraceBuilder.add(alphabet.getSymbol(random.nextInt(alphabetSize)));
+                Assert.assertNotNull(trans);
+                Assert.assertNotNull(hypothesis.getSuccessor(trans));
             }
-
-            // simply try to compute output without an exception
-            hypothesis.computeOutput(testTraceBuilder.toWord());
         }
     }
 
diff --git a/test-support/learning-examples/pom.xml b/test-support/learning-examples/pom.xml
index 57bd2a1fd7..a94aa2e453 100644
--- a/test-support/learning-examples/pom.xml
+++ b/test-support/learning-examples/pom.xml
@@ -21,7 +21,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-test-support-parent</artifactId>
         <groupId>de.learnlib.testsupport</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/test-support/pom.xml b/test-support/pom.xml
index c80801fe0d..4c957acbb7 100644
--- a/test-support/pom.xml
+++ b/test-support/pom.xml
@@ -21,7 +21,7 @@ limitations under the License.
     <parent>
         <artifactId>learnlib-build-parent</artifactId>
         <groupId>de.learnlib</groupId>
-        <version>0.13.0</version>
+        <version>0.13.1</version>
         <relativePath>../build-parent/pom.xml</relativePath>
     </parent>