--- hw/xfree86/common/xf86Helper.c.orig	2020-08-25 12:39:55.000000000 -0300
+++ hw/xfree86/common/xf86Helper.c	2020-11-24 17:47:49.756689000 -0300
@@ -728,9 +728,9 @@
         scrp->mask.red = mask.red;
         scrp->mask.green = mask.green;
         scrp->mask.blue = mask.blue;
-        scrp->offset.red = ffs(mask.red);
-        scrp->offset.green = ffs(mask.green);
-        scrp->offset.blue = ffs(mask.blue);
+        scrp->offset.red = ffs(mask.red) - 1;
+        scrp->offset.green = ffs(mask.green) - 1;
+        scrp->offset.blue = ffs(mask.blue) - 1;
     }
     return TRUE;
 }