diff --git a/src/proto/mbyte.pro b/src/proto/mbyte.pro
index 88f14f4..11b6443 100644
--- a/src/proto/mbyte.pro
+++ b/src/proto/mbyte.pro
@@ -45,6 +45,7 @@
 int dbcs_head_off __ARGS((char_u *base, char_u *p));
 int dbcs_screen_head_off __ARGS((char_u *base, char_u *p));
 int utf_head_off __ARGS((char_u *base, char_u *p));
+void mb_copy_char __ARGS((char_u **fp, char_u **tp));
 int mb_off_next __ARGS((char_u *base, char_u *p));
 int mb_tail_off __ARGS((char_u *base, char_u *p));
 int utf_valid_string __ARGS((char_u *s, char_u *end));