diff --git a/nx-X11/programs/Xserver/hw/nxagent/Window.c b/nx-X11/programs/Xserver/hw/nxagent/Window.c
index 0a8e8c2..3603a05 100644
--- a/nx-X11/programs/Xserver/hw/nxagent/Window.c
+++ b/nx-X11/programs/Xserver/hw/nxagent/Window.c
@@ -335,7 +335,10 @@ FIXME: We need to set save under on the real display?
 
   if (mask & CWEventMask)
   {
-    nxagentGetEventMask(pWin, (Mask*)&attributes.event_mask);
+    /* Assume that the mask fits in int... broken on Big Endian 64bit systems. */
+    Mask tmp_mask = attributes.event_mask;
+    nxagentGetEventMask(pWin, &tmp_mask);
+    attributes.event_mask = (int)tmp_mask;
   }
   #ifdef WARNING
   else