diff --git a/src/proto/spell.pro b/src/proto/spell.pro
index 4a3e85b..55c8482 100644
--- a/src/proto/spell.pro
+++ b/src/proto/spell.pro
@@ -5,6 +5,7 @@
 int match_compoundrule(slang_T *slang, char_u *compflags);
 int valid_word_prefix(int totprefcnt, int arridx, int flags, char_u *word, slang_T *slang, int cond_req);
 int spell_valid_case(int wordflags, int treeflags);
+int spell_check_window(win_T *wp);
 int spell_move_to(win_T *wp, int dir, int allwords, int curline, hlf_T *attrp);
 void spell_cat_line(char_u *buf, char_u *line, int maxlen);
 char_u *spell_enc(void);