diff --git a/gtk2_ardour/cocoacarbon.mm b/gtk2_ardour/cocoacarbon.mm
index 6564843972..e26bd5788c 100644
--- a/gtk2_ardour/cocoacarbon.mm
+++ b/gtk2_ardour/cocoacarbon.mm
@@ -29,6 +29,8 @@
 #undef verify
 #endif
 
+#undef Nil // ardour_ui.h ->  window_manager.h -> lua_script_manager.h -> ardour/luascripting.h -> ... lua  uses Nil
+
 #include "ardour_ui.h"
 #include "actions.h"
 #include "opts.h"