diff --git a/widget/src/gtk2/nsWindow.cpp b/widget/src/gtk2/nsWindow.cpp
index b6a482fcbb87..a7f71577bfe8 100644
--- a/widget/src/gtk2/nsWindow.cpp
+++ b/widget/src/gtk2/nsWindow.cpp
@@ -2155,6 +2155,10 @@ nsWindow::NativeCreate(nsIWidget        *aParent,
 
             mDrawingarea = moz_drawingarea_new(nsnull, mContainer);
         }
+        else {
+            NS_WARNING("Warning: tried to create a new child widget with no parent!");
+            return NS_ERROR_FAILURE;
+        }
     }
         break;
     default: