diff --git a/src/proto/typval.pro b/src/proto/typval.pro
index f5804a3..f04bf15 100644
--- a/src/proto/typval.pro
+++ b/src/proto/typval.pro
@@ -40,6 +40,7 @@
 int check_for_string_or_number_or_list_arg(typval_T *args, int idx);
 int check_for_opt_string_or_number_or_list_arg(typval_T *args, int idx);
 int check_for_string_or_list_or_dict_arg(typval_T *args, int idx);
+int check_for_string_or_func_arg(typval_T *args, int idx);
 int check_for_list_or_blob_arg(typval_T *args, int idx);
 int check_for_list_or_dict_arg(typval_T *args, int idx);
 int check_for_list_or_dict_or_blob_arg(typval_T *args, int idx);