diff --git a/src/proto/mbyte.pro b/src/proto/mbyte.pro
index 16a36c8..ef11dc7 100644
--- a/src/proto/mbyte.pro
+++ b/src/proto/mbyte.pro
@@ -12,9 +12,9 @@
 int utf_ptr2cells __ARGS((char_u *p));
 int dbcs_ptr2cells __ARGS((char_u *p));
 int latin_char2cells __ARGS((int c));
-int latin_off2cells __ARGS((unsigned off));
-int dbcs_off2cells __ARGS((unsigned off));
-int utf_off2cells __ARGS((unsigned off));
+int latin_off2cells __ARGS((unsigned off, unsigned max_off));
+int dbcs_off2cells __ARGS((unsigned off, unsigned max_off));
+int utf_off2cells __ARGS((unsigned off, unsigned max_off));
 int latin_ptr2char __ARGS((char_u *p));
 int utf_ptr2char __ARGS((char_u *p));
 int mb_ptr2char_adv __ARGS((char_u **pp));