--- xorg-server-1.20.1.orig/hw/xwin/winwindow.c	2018-08-07 18:31:04.000000000 +0200
+++ xorg-server-1.20.1/hw/xwin/winwindow.c	2018-08-22 19:39:37.078925268 +0200
@@ -269,14 +269,14 @@
 
             if (pWinPriv->hRgn) {
                 if (CombineRgn(hRgnWin, hRgnWin, pWinPriv->hRgn, RGN_AND)
-                    == ERROR) {
+                    == 0) {
                     ErrorF("winAddRgn - CombineRgn () failed\n");
                 }
             }
 
             OffsetRgn(hRgnWin, iX, iY);
 
-            if (CombineRgn(hRgn, hRgn, hRgnWin, RGN_OR) == ERROR) {
+            if (CombineRgn(hRgn, hRgn, hRgnWin, RGN_OR) == 0) {
                 ErrorF("winAddRgn - CombineRgn () failed\n");
             }
 
@@ -363,7 +363,7 @@
             }
 
             /* Merge the Windows region with the accumulated region */
-            if (CombineRgn(hRgn, hRgn, hRgnRect, RGN_OR) == ERROR) {
+            if (CombineRgn(hRgn, hRgn, hRgnRect, RGN_OR) == 0) {
                 ErrorF("winReshapeRootless - CombineRgn() failed\n");
             }