diff --git a/reactos/subsys/win32k/eng/bitblt.c b/reactos/subsys/win32k/eng/bitblt.c
index edd4835eec4..532974773d8 100644
--- a/reactos/subsys/win32k/eng/bitblt.c
+++ b/reactos/subsys/win32k/eng/bitblt.c
@@ -16,7 +16,7 @@
  *  along with this program; if not, write to the Free Software
  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
-/* $Id: bitblt.c,v 1.42 2004/02/24 13:27:02 weiden Exp $
+/* $Id: bitblt.c,v 1.43 2004/03/22 14:58:56 weiden Exp $
  *
  * COPYRIGHT:        See COPYING in the top level directory
  * PROJECT:          ReactOS kernel
@@ -892,7 +892,7 @@ AlphaBltMask(SURFOBJ* Dest,
       g = (int)GetGValue(BrushColor);
       b = (int)GetBValue(BrushColor);
       
-      tMask = Mask->pvBits + MaskPoint->y * Mask->lDelta + MaskPoint->x;
+      tMask = Mask->pvBits + (SourcePoint->y * Mask->lDelta) + SourcePoint->x;
       for (j = 0; j < dy; j++)
 	{
 	  lMask = tMask;