diff --git a/wmlib/WMaker.h b/wmlib/WMaker.h
index 1c2a8b26..9e4009e0 100644
--- a/wmlib/WMaker.h
+++ b/wmlib/WMaker.h
@@ -24,6 +24,8 @@
 /* the definitions in this file can change at any time. WINGs has more
  * stable definitions */
 
+#undef BOOL
+
 #include <X11/Xlib.h>
 #include <X11/Xmd.h>