diff --git a/src/proto/vim9script.pro b/src/proto/vim9script.pro
index 6a32abd..f8b12ee 100644
--- a/src/proto/vim9script.pro
+++ b/src/proto/vim9script.pro
@@ -1,6 +1,7 @@
 /* vim9script.c */
 int in_vim9script(void);
 void ex_vim9script(exarg_T *eap);
+int not_in_vim9(exarg_T *eap);
 void ex_export(exarg_T *eap);
 void free_imports(int sid);
 void ex_import(exarg_T *eap);