diff --git a/src/proto/vim9script.pro b/src/proto/vim9script.pro
index c80618f..a7d821c 100644
--- a/src/proto/vim9script.pro
+++ b/src/proto/vim9script.pro
@@ -2,6 +2,7 @@
 int in_vim9script(void);
 void ex_vim9script(exarg_T *eap);
 int not_in_vim9(exarg_T *eap);
+int vim9_bad_comment(char_u *p);
 int vim9_comment_start(char_u *p);
 void ex_export(exarg_T *eap);
 void free_imports_and_script_vars(int sid);