diff --git a/src/proto.h b/src/proto.h
index 4c0db37..6116578 100644
--- a/src/proto.h
+++ b/src/proto.h
@@ -261,6 +261,10 @@
 # include "if_perlsfio.pro"
 #endif
 
+#if defined(FEAT_MBYTE) && defined(MACOS_X)
+# include "os_mac_conv.pro"
+#endif
+
 #ifdef __BORLANDC__
 # define _PROTO_H
 #endif