diff --git a/src/proto/screen.pro b/src/proto/screen.pro
index 66fc0f3..81e5e10 100644
--- a/src/proto/screen.pro
+++ b/src/proto/screen.pro
@@ -56,4 +56,5 @@
 int screen_screencol(void);
 int screen_screenrow(void);
 char *set_chars_option(win_T *wp, char_u **varp, int apply);
+char *check_chars_options(void);
 /* vim: set ft=c : */