--- a/layout/tables/nsTableRowGroupFrame.cpp
+++ b/layout/tables/nsTableRowGroupFrame.cpp
@@ -919,29 +919,21 @@ nsTableRowGroupFrame::CollapseRowGroupIf
                                               groupRect.height));
   nsTableFrame::RePositionViews(this);
   nsTableFrame::InvalidateFrame(this, oldGroupRect, oldGroupOverflowRect,
                                 PR_FALSE);
 
   return yGroupOffset;
 }
 
-// Move a child that was skipped during an incremental reflow.
-// This function is not used for paginated mode so we don't need to deal
-// with continuing frames, and it's only called if aKidFrame has no
-// cells that span into it and no cells that span across it. That way
-// we don't have to deal with rowspans
-// XXX Is it still true that it's not used for paginated mode?
+// Move a child that was skipped during a reflow.
 void
 nsTableRowGroupFrame::SlideChild(nsRowGroupReflowState& aReflowState,
                                  nsIFrame*              aKidFrame)
 {
-  NS_PRECONDITION(NS_UNCONSTRAINEDSIZE == aReflowState.reflowState.availableHeight,
-                  "we're not in galley mode");
-
   // Move the frame if we need to
   nsPoint oldPosition = aKidFrame->GetPosition();
   nsPoint newPosition = oldPosition;
   newPosition.y = aReflowState.y;
   if (oldPosition.y != newPosition.y) {
     aKidFrame->InvalidateOverflowRect();
     aKidFrame->SetPosition(newPosition);
     nsTableFrame::RePositionViews(aKidFrame);