diff --git a/oppl2plugin/src/main/java/org/coode/patterns/protege/ui/PatternModelList.java b/oppl2plugin/src/main/java/org/coode/patterns/protege/ui/PatternModelList.java
index 06ccde43..68701f47 100644
--- a/oppl2plugin/src/main/java/org/coode/patterns/protege/ui/PatternModelList.java
+++ b/oppl2plugin/src/main/java/org/coode/patterns/protege/ui/PatternModelList.java
@@ -272,7 +272,7 @@ public void setRootObject(PatternAnnotationContainer root) {
 
     @Override
     protected List<MListButton> getListItemButtons(MListItem item) {
-        List<MListButton> listItemButtons = super.getListItemButtons(item);
+        List<MListButton> listItemButtons = new ArrayList<MListButton>(super.getListItemButtons(item));
         if (item instanceof PatternListItem) {
             final PatternModel patternModel = ((PatternListItem) item).getPatternModel();
             if (!patternModel.isClassPattern()) {