diff --git a/src/proto/evalvars.pro b/src/proto/evalvars.pro
index 9879a40..ea14fe5 100644
--- a/src/proto/evalvars.pro
+++ b/src/proto/evalvars.pro
@@ -77,7 +77,7 @@
 void delete_var(hashtab_T *ht, hashitem_T *hi);
 int before_set_vvar(char_u *varname, dictitem_T *di, typval_T *tv, int copy, int *type_error);
 void set_var(char_u *name, typval_T *tv, int copy);
-void set_var_const(char_u *name, scid_T sid, type_T *type_arg, typval_T *tv_arg, int copy, int flags_arg, int var_idx);
+int set_var_const(char_u *name, scid_T sid, type_T *type_arg, typval_T *tv_arg, int copy, int flags_arg, int var_idx);
 int var_check_permission(dictitem_T *di, char_u *name);
 int var_check_ro(int flags, char_u *name, int use_gettext);
 int var_check_lock(int flags, char_u *name, int use_gettext);