diff --git a/src/proto/mbyte.pro b/src/proto/mbyte.pro
index 9385d85..7a6009e 100644
--- a/src/proto/mbyte.pro
+++ b/src/proto/mbyte.pro
@@ -85,4 +85,5 @@
 char_u *string_convert(vimconv_T *vcp, char_u *ptr, int *lenp);
 char_u *string_convert_ext(vimconv_T *vcp, char_u *ptr, int *lenp, int *unconvlenp);
 void f_setcellwidths(typval_T *argvars, typval_T *rettv);
+void f_charclass(typval_T *argvars, typval_T *rettv);
 /* vim: set ft=c : */