diff --git a/query/plugins/org.eclipse.viatra.query.runtime/src/org/eclipse/viatra/query/runtime/registry/view/AbstractRegistryView.java b/query/plugins/org.eclipse.viatra.query.runtime/src/org/eclipse/viatra/query/runtime/registry/view/AbstractRegistryView.java
index f8121492f4..b5b011671c 100644
--- a/query/plugins/org.eclipse.viatra.query.runtime/src/org/eclipse/viatra/query/runtime/registry/view/AbstractRegistryView.java
+++ b/query/plugins/org.eclipse.viatra.query.runtime/src/org/eclipse/viatra/query/runtime/registry/view/AbstractRegistryView.java
@@ -109,11 +109,13 @@ public Set<IQuerySpecificationRegistryEntry> getEntries(String fullyQualifiedNam
 
     @Override
     public void addViewListener(IQuerySpecificationRegistryChangeListener listener) {
+        checkArgument(listener != null, "Null listener not supported");
         listeners.add(listener);
     }
 
     @Override
     public void removeViewListener(IQuerySpecificationRegistryChangeListener listener) {
+        checkArgument(listener != null, "Null listener not supported");
         listeners.remove(listener);
     }
 
diff --git a/query/plugins/org.eclipse.viatra.query.tooling.ui.browser/src/org/eclipse/viatra/query/tooling/ui/queryregistry/QueryRegistryTreeInput.xtend b/query/plugins/org.eclipse.viatra.query.tooling.ui.browser/src/org/eclipse/viatra/query/tooling/ui/queryregistry/QueryRegistryTreeInput.xtend
index acd8acc09a..36768383c1 100644
--- a/query/plugins/org.eclipse.viatra.query.tooling.ui.browser/src/org/eclipse/viatra/query/tooling/ui/queryregistry/QueryRegistryTreeInput.xtend
+++ b/query/plugins/org.eclipse.viatra.query.tooling.ui.browser/src/org/eclipse/viatra/query/tooling/ui/queryregistry/QueryRegistryTreeInput.xtend
@@ -39,7 +39,7 @@ class QueryRegistryTreeInput {
     @Accessors(PUBLIC_GETTER)
     IRegistryView view
     
-    @Accessors(PUBLIC_GETTER, PUBLIC_SETTER)
+    @Accessors(PUBLIC_GETTER)
     IQuerySpecificationRegistryChangeListener listener
     
     new(IQuerySpecificationRegistry registry) {
@@ -57,7 +57,16 @@ class QueryRegistryTreeInput {
             val entry = new QueryRegistryTreeEntry(treePackage.pckg, it)
             treePackage.pckg.entries.put(fullyQualifiedName, entry)
         ]
-        view.addViewListener(listener)
+    }
+    
+    def void setListener(IQuerySpecificationRegistryChangeListener listener) {
+        if (this.listener !== null) {
+            view.removeViewListener(this.listener)
+        }
+        this.listener = listener
+        if (listener !== null) {
+            view.addViewListener(listener)
+        }
     }
     
     def QueryRegistryTreeInputChange addEntryToInput(IQuerySpecificationRegistryEntry entry) {