diff --git a/src/proto/spell.pro b/src/proto/spell.pro
index 15a68a6..2771a90 100644
--- a/src/proto/spell.pro
+++ b/src/proto/spell.pro
@@ -1,6 +1,7 @@
 /* spell.c */
 int spell_check __ARGS((win_T *wp, char_u *ptr, int *attrp));
 int spell_move_to __ARGS((int dir, int allwords, int curline));
+void spell_cat_line __ARGS((char_u *buf, char_u *line, int maxlen));
 char_u *did_set_spelllang __ARGS((buf_T *buf));
 void spell_reload __ARGS((void));
 void put_bytes __ARGS((FILE *fd, long_u nr, int len));