diff --git a/spanner/src/read_stale_data.php b/spanner/src/read_stale_data.php
index 52581ffca0..c9b09da1f5 100644
--- a/spanner/src/read_stale_data.php
+++ b/spanner/src/read_stale_data.php
@@ -48,7 +48,7 @@ function read_stale_data($instanceId, $databaseId)
         'Albums',
         $keySet,
         ['SingerId', 'AlbumId', 'AlbumTitle'],
-        ['exactStaleness' => new Duration(10)]
+        ['exactStaleness' => new Duration(15)]
     );
 
     foreach ($results->rows() as $row) {
diff --git a/spanner/test/spannerTest.php b/spanner/test/spannerTest.php
index 11896e4f22..fcd78e5c0c 100644
--- a/spanner/test/spannerTest.php
+++ b/spanner/test/spannerTest.php
@@ -223,11 +223,11 @@ public function testReadOnlyTransaction()
      */
     public function testReadStaleData()
     {
-        // read-stale-data reads data that is exactly 10 seconds old.  So, make sure 10 seconds
+        // read-stale-data reads data that is exactly 15 seconds old.  So, make sure 15 seconds
         // have elapsed since testUpdateData().
         $elapsed = time() - self::$lastUpdateDataTimestamp;
-        if ($elapsed < 11) {
-            sleep(11 - $elapsed);
+        if ($elapsed < 16) {
+            sleep(16 - $elapsed);
         }
         $output = $this->runCommand('read-stale-data');
         $this->assertContains('SingerId: 1, AlbumId: 1, AlbumTitle: Go, Go, Go', $output);