diff --git a/src/Cache/ShsTermCacheDependency.php b/src/Cache/ShsTermCacheDependency.php
index 2b8c5aa4a39da3f39def4accb74fb28f48eb3a87..a8e6be76b067f51f01ff4d025f4b9d723f736129 100644
--- a/src/Cache/ShsTermCacheDependency.php
+++ b/src/Cache/ShsTermCacheDependency.php
@@ -66,10 +66,18 @@ class ShsTermCacheDependency implements CacheableDependencyInterface {
     $list_cache_tags = $entity_type->getListCacheTags();
 
     if ($this->bundle !== NULL) {
-      $list_cache_tags = Cache::mergeTags(
-        $list_cache_tags,
-        $entity_type->getBundleListCacheTags($this->bundle),
-      );
+      // EntityType::getBundleListCacheTags() was added in Drupal core 11.x
+      // (see https://www.drupal.org/node/3512328) and does not exist on
+      // Drupal 10.x. Fall back to the documented "ENTITY_TYPE_list:BUNDLE"
+      // cache tag format there instead of triggering a fatal error.
+      if (method_exists($entity_type, 'getBundleListCacheTags')) {
+        $bundle_list_cache_tags = $entity_type->getBundleListCacheTags($this->bundle);
+      }
+      else {
+        $bundle_list_cache_tags = [$entity_type->id() . '_list:' . $this->bundle];
+      }
+
+      $list_cache_tags = Cache::mergeTags($list_cache_tags, $bundle_list_cache_tags);
     }
 
     return Cache::mergeTags($this->tags, $list_cache_tags);
diff --git a/src/Plugin/Field/FieldWidget/OptionsShsWidget.php b/src/Plugin/Field/FieldWidget/OptionsShsWidget.php
index 2cdfda3de204eafb0d51a7a6fb63ed51e89ec262..a2bc28018063bc96e57503964e298e3ea0b3b9b3 100644
--- a/src/Plugin/Field/FieldWidget/OptionsShsWidget.php
+++ b/src/Plugin/Field/FieldWidget/OptionsShsWidget.php
@@ -180,10 +180,10 @@ class OptionsShsWidget extends OptionsSelectWidget implements ContainerFactoryPl
       $value = NestedArray::getValue($user_input, $field_parents);
       $default_value = $value ?: $default_value;
     }
-    elseif (isset($user_input[$field_name]) && strpos($user_input[$field_name], ',') !== FALSE) {
+    elseif (isset($user_input[$field_name]) && is_string($user_input[$field_name]) && strpos($user_input[$field_name], ',') !== FALSE) {
       $default_value = explode(',', $user_input[$field_name]);
     }
-    elseif (isset($user_input[$field_name]) && strpos(trim($user_input[$field_name]), ' ') !== FALSE) {
+    elseif (isset($user_input[$field_name]) && is_string($user_input[$field_name]) && strpos(trim($user_input[$field_name]), ' ') !== FALSE) {
       $default_value = explode(' ', $user_input[$field_name]);
     }
     elseif (isset($user_input[$field_name])) {