diff --git a/src/proto/vim9execute.pro b/src/proto/vim9execute.pro
index ef22af7..6f42fc8 100644
--- a/src/proto/vim9execute.pro
+++ b/src/proto/vim9execute.pro
@@ -1,6 +1,7 @@
 /* vim9execute.c */
 void to_string_error(vartype_T vartype);
 void funcstack_check_refcount(funcstack_T *funcstack);
+int set_ref_in_funcstacks(int copyID);
 char_u *char_from_string(char_u *str, varnumber_T index);
 char_u *string_slice(char_u *str, varnumber_T first, varnumber_T last, int exclusive);
 int fill_partial_and_closure(partial_T *pt, ufunc_T *ufunc, ectx_T *ectx);