diff --git a/layout/html/table/src/nsTableRowGroupFrame.cpp b/layout/html/table/src/nsTableRowGroupFrame.cpp
index 846c43f02fc8..01f4d53da847 100644
--- a/layout/html/table/src/nsTableRowGroupFrame.cpp
+++ b/layout/html/table/src/nsTableRowGroupFrame.cpp
@@ -1767,6 +1767,9 @@ nsTableRowGroupFrame::GetLine(PRInt32 aLineNumber, nsIFrame** aFirstFrameOnLine,
   // not gonna touch aLineBounds right now
 
   CellData* firstCellData = cellMap->GetCellAt(aLineNumber, 0);
+  if(!firstCellData) 
+    return NS_ERROR_FAILURE;
+
   *aFirstFrameOnLine = (nsIFrame*)firstCellData->GetCellFrame();
   if(!(*aFirstFrameOnLine))
   {
diff --git a/layout/tables/nsTableRowGroupFrame.cpp b/layout/tables/nsTableRowGroupFrame.cpp
index 846c43f02fc8..01f4d53da847 100644
--- a/layout/tables/nsTableRowGroupFrame.cpp
+++ b/layout/tables/nsTableRowGroupFrame.cpp
@@ -1767,6 +1767,9 @@ nsTableRowGroupFrame::GetLine(PRInt32 aLineNumber, nsIFrame** aFirstFrameOnLine,
   // not gonna touch aLineBounds right now
 
   CellData* firstCellData = cellMap->GetCellAt(aLineNumber, 0);
+  if(!firstCellData) 
+    return NS_ERROR_FAILURE;
+
   *aFirstFrameOnLine = (nsIFrame*)firstCellData->GetCellFrame();
   if(!(*aFirstFrameOnLine))
   {