diff --git a/dom/src/base/nsGlobalWindow.cpp b/dom/src/base/nsGlobalWindow.cpp
index f931c83ac65..da3f57a64ce 100644
--- a/dom/src/base/nsGlobalWindow.cpp
+++ b/dom/src/base/nsGlobalWindow.cpp
@@ -883,7 +883,7 @@ NS_IMETHODIMP GlobalWindowImpl::SetInnerHeight(PRInt32 aInnerHeight)
    if(!docShellParent) 
       {
       nsCOMPtr<nsIDocShellTreeOwner> treeOwner;
-      docShellParent->GetTreeOwner(getter_AddRefs(treeOwner));
+      docShellAsItem->GetTreeOwner(getter_AddRefs(treeOwner));
       NS_ENSURE_TRUE(treeOwner, NS_ERROR_FAILURE);
 
       nsCOMPtr<nsIBaseWindow> docShellAsWin(do_QueryInterface(mDocShell));