1 files changed, 1 insertions, 1 deletions

diff --git a/subprojects/store/src/main/java/tools/refinery/store/map/VersionedMapStoreDeltaImpl.java b/subprojects/store/src/main/java/tools/refinery/store/map/VersionedMapStoreDeltaImpl.java
index e556a8bb..f41a2d75 100644
--- a/subprojects/store/src/main/java/tools/refinery/store/map/VersionedMapStoreDeltaImpl.java
+++ b/subprojects/store/src/main/java/tools/refinery/store/map/VersionedMapStoreDeltaImpl.java
@@ -78,7 +78,7 @@ public class VersionedMapStoreDeltaImpl<K, V> implements VersionedMapStore<K, V>
 
         @Override
         public synchronized Set<Long> getStates() {
-                return states.keySet();
+                return new HashSet<>(states.keySet());
         }
 
         @Override