diff --git a/layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp b/layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp
index bb5393173b3e..0a0ce424b11b 100644
--- a/layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp
+++ b/layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp
@@ -634,9 +634,20 @@ nsTreeBodyFrame::ReflowFinished(nsIPresShell* aPresShell, PRBool* aFlushFlag)
     PRInt32 rowCount;
     mView->GetRowCount(&rowCount);
     PRInt32 lastPageTopRow = PR_MAX(0, rowCount - mPageCount);
-    if (mTopRowIndex >= lastPageTopRow)
+    if (mTopRowIndex > lastPageTopRow)
       ScrollToRow(lastPageTopRow);
 
+    // make sure that the current selected item is still
+    // visible after the tree changes size.
+    nsCOMPtr<nsITreeSelection> sel;
+    mView->GetSelection(getter_AddRefs(sel));
+    if (sel) {
+      PRInt32 currentIndex;
+      sel->GetCurrentIndex(&currentIndex);
+      if (currentIndex != -1)
+        EnsureRowIsVisible(currentIndex);
+    }
+
     InvalidateScrollbar();
     CheckVerticalOverflow();
   }