diff --git a/simgear/canvas/elements/CanvasGroup.cxx b/simgear/canvas/elements/CanvasGroup.cxx
index c753c2e2..d398fe2e 100644
--- a/simgear/canvas/elements/CanvasGroup.cxx
+++ b/simgear/canvas/elements/CanvasGroup.cxx
@@ -387,7 +387,9 @@ namespace canvas
     OSGUserData* ud =
       static_cast<OSGUserData*>(_transform->getChild(index)->getUserData());
     assert(ud);
-    return ud->element;
+    if (ud)
+        return ud->element;
+    return nullptr;
   }
 
   //----------------------------------------------------------------------------