diff --git a/src/proto/vim9script.pro b/src/proto/vim9script.pro
index 2c4bd79..41bf128 100644
--- a/src/proto/vim9script.pro
+++ b/src/proto/vim9script.pro
@@ -18,4 +18,5 @@
 void free_all_script_vars(scriptitem_T *si);
 svar_T *find_typval_in_script(typval_T *dest);
 int check_script_var_type(typval_T *dest, typval_T *value, char_u *name, where_T where);
+int check_reserved_name(char_u *name);
 /* vim: set ft=c : */