diff --git a/cura/OneAtATimeIterator.py b/cura/OneAtATimeIterator.py
index 755680e62f..5653c8f1fb 100644
--- a/cura/OneAtATimeIterator.py
+++ b/cura/OneAtATimeIterator.py
@@ -18,7 +18,7 @@ class OneAtATimeIterator(Iterator.Iterator):
     def _fillStack(self):
         node_list = []
         for node in self._scene_node.getChildren():
-            if not issubclass(type(node), SceneNode):
+            if not isinstance(node, SceneNode):
                 continue
 
             if node.callDecoration("getConvexHull"):