diff --git a/src/proto/spell.pro b/src/proto/spell.pro
index 680bf34..a68de8f 100644
--- a/src/proto/spell.pro
+++ b/src/proto/spell.pro
@@ -45,6 +45,6 @@
 int expand_spelling(linenr_T lnum, char_u *pat, char_u ***matchp);
 int valid_spelllang(char_u *val);
 int valid_spellfile(char_u *val);
-char *did_set_spell_option(int is_spellfile);
+char *did_set_spell_option(void);
 char *compile_cap_prog(synblock_T *synblock);
 /* vim: set ft=c : */