diff --git a/src/proto.h b/src/proto.h
index c39f7f0..d9c0091 100644
--- a/src/proto.h
+++ b/src/proto.h
@@ -174,6 +174,10 @@
 # include "version.pro"
 # include "window.pro"
 
+# ifdef FEAT_LUA
+#  include "if_lua.pro"
+# endif
+
 # ifdef FEAT_MZSCHEME
 #  include "if_mzsch.pro"
 # endif