diff --git a/src/proto/strings.pro b/src/proto/strings.pro
index aa8b374..b792edc 100644
--- a/src/proto/strings.pro
+++ b/src/proto/strings.pro
@@ -15,6 +15,7 @@
 size_t vim_strlen_maxlen(char *s, size_t maxlen);
 int vim_stricmp(char *s1, char *s2);
 int vim_strnicmp(char *s1, char *s2, size_t len);
+int vim_strnicmp_asc(char *s1, char *s2, size_t len);
 char_u *vim_strchr(char_u *string, int c);
 char_u *vim_strbyte(char_u *string, int c);
 char_u *vim_strrchr(char_u *string, int c);