diff --git a/widget/src/windows/nsWindow.cpp b/widget/src/windows/nsWindow.cpp
index 653e6c5ae938..9d85c4a773f7 100644
--- a/widget/src/windows/nsWindow.cpp
+++ b/widget/src/windows/nsWindow.cpp
@@ -5835,9 +5835,11 @@ nsWindow::ClientMarginHitTestPoint(PRInt32 mx, PRInt32 my)
   else if (my < winRect.bottom && my >= (winRect.bottom - mVertResizeMargin))
     bottom = PR_TRUE;
 
-  if (mx >= winRect.left && mx < (winRect.left + mHorResizeMargin))
+  if (mx >= winRect.left && mx < (winRect.left +
+                                  (bottom ? (2*mHorResizeMargin) : mHorResizeMargin)))
     left = PR_TRUE;
-  else if (mx < winRect.right && mx >= (winRect.right - mHorResizeMargin))
+  else if (mx < winRect.right && mx >= (winRect.right -
+                                        (bottom ? (2*mHorResizeMargin) : mHorResizeMargin)))
     right = PR_TRUE;
 
   if (top) {