diff --git a/src/proto/mbyte.pro b/src/proto/mbyte.pro
index c57c94c..bb976e3 100644
--- a/src/proto/mbyte.pro
+++ b/src/proto/mbyte.pro
@@ -48,6 +48,7 @@
 int utf_tolower(int a);
 int utf_isupper(int a);
 int mb_strnicmp(char_u *s1, char_u *s2, size_t nn);
+int mb_strnicmp2(char_u *s1, char_u *s2, size_t n1, size_t n2);
 void show_utf8(void);
 int latin_head_off(char_u *base, char_u *p);
 int dbcs_screen_head_off(char_u *base, char_u *p);