diff --git a/src/proto/window.pro b/src/proto/window.pro
index 441070e..4ab7103 100644
--- a/src/proto/window.pro
+++ b/src/proto/window.pro
@@ -98,7 +98,7 @@
 int win_hasvertsplit(void);
 int get_win_number(win_T *wp, win_T *first_win);
 int get_tab_number(tabpage_T *tp);
-char *check_colorcolumn(win_T *wp);
+char *check_colorcolumn(char_u *cc, win_T *wp);
 int get_last_winid(void);
 int win_locked(win_T *wp);
 /* vim: set ft=c : */