diff --git a/Scripts/Editor/NodeEditorWindow.cs b/Scripts/Editor/NodeEditorWindow.cs
index 1f64653..4fc1136 100644
--- a/Scripts/Editor/NodeEditorWindow.cs
+++ b/Scripts/Editor/NodeEditorWindow.cs
@@ -97,7 +97,7 @@ namespace XNodeEditor {
         /// <summary> Make sure the graph editor is assigned and to the right object </summary>
         private void ValidateGraphEditor() {
             NodeGraphEditor graphEditor = NodeGraphEditor.GetEditor(graph, this);
-            if (this.graphEditor != graphEditor) {
+            if (this.graphEditor != graphEditor && graphEditor != null) {
                 this.graphEditor = graphEditor;
                 graphEditor.OnOpen();
             }