diff --git a/layout/xul/base/src/nsXULTreeSliceFrame.cpp b/layout/xul/base/src/nsXULTreeSliceFrame.cpp
index 80892b747e08..38266fb6a9fd 100644
--- a/layout/xul/base/src/nsXULTreeSliceFrame.cpp
+++ b/layout/xul/base/src/nsXULTreeSliceFrame.cpp
@@ -79,11 +79,11 @@ nsXULTreeSliceFrame::Release(void)
 //
 NS_INTERFACE_MAP_BEGIN(nsXULTreeSliceFrame)
   NS_INTERFACE_MAP_ENTRY(nsIXULTreeSlice)
-NS_INTERFACE_MAP_END_INHERITING(nsBoxFrame)
+NS_INTERFACE_MAP_END_INHERITING(nsGridRowLeafFrame)
 
 // Constructor
 nsXULTreeSliceFrame::nsXULTreeSliceFrame(nsIPresShell* aPresShell, PRBool aIsRoot, nsIBoxLayout* aLayoutManager)
-:nsBoxFrame(aPresShell, aIsRoot, aLayoutManager) 
+:nsGridRowLeafFrame(aPresShell, aIsRoot, aLayoutManager) 
 {}
 
 // Destructor
@@ -94,7 +94,7 @@ nsXULTreeSliceFrame::~nsXULTreeSliceFrame()
 nsresult
 nsXULTreeSliceFrame::GetPrefSize(nsBoxLayoutState& aState, nsSize& aSize)
 {
-  nsresult rv = nsBoxFrame::GetPrefSize(aState, aSize);
+  nsresult rv = nsGridRowLeafFrame::GetPrefSize(aState, aSize);
   if (NS_FAILED(rv)) return rv;
 
   aSize.height = PR_MAX(mRect.height, aSize.height);
diff --git a/layout/xul/base/src/nsXULTreeSliceFrame.h b/layout/xul/base/src/nsXULTreeSliceFrame.h
index fa10b013b633..fb45893d3d06 100644
--- a/layout/xul/base/src/nsXULTreeSliceFrame.h
+++ b/layout/xul/base/src/nsXULTreeSliceFrame.h
@@ -36,15 +36,10 @@
  *
  * ***** END LICENSE BLOCK ***** */
 
-#include "nsBoxFrame.h"
 #include "nsIXULTreeSlice.h"
-
-#ifdef MOZ_GRID2
 #include "nsGridRowLeafFrame.h"
+
 class nsXULTreeSliceFrame : public nsGridRowLeafFrame, public nsIXULTreeSlice
-#else
-class nsXULTreeSliceFrame : public nsBoxFrame, public nsIXULTreeSlice
-#endif
 {
 public:
   NS_DECL_ISUPPORTS