--- a/layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp
+++ b/layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp
@@ -855,16 +855,17 @@ FindScrollParts(nsIFrame* aCurrFrame, ns
       }
     }
     // don't bother searching inside a scrollbar
     return;
   }
   
   nsIFrame* child = aCurrFrame->GetFirstChild(nsnull);
   while (child &&
+         !child->GetContent()->IsRootOfNativeAnonymousSubtree() &&
          (!aResult->mVScrollbar || !aResult->mHScrollbar ||
           !aResult->mColumnsScrollFrame)) {
     FindScrollParts(child, aResult);
     child = child->GetNextSibling();
   }
 }
 
 nsTreeBodyFrame::ScrollParts nsTreeBodyFrame::GetScrollParts()