diff --git a/layout/base/public/nsIStyleContext.h b/layout/base/public/nsIStyleContext.h
index f7bb59ca844..3e857a859e3 100644
--- a/layout/base/public/nsIStyleContext.h
+++ b/layout/base/public/nsIStyleContext.h
@@ -221,6 +221,7 @@ struct nsBorderEdges
 {
   nsVoidArray mEdges[4];
   nsMargin    mMaxBorderWidth;
+  PRBool      mOutsideEdge;
 
   nsBorderEdges();
 };