diff --git a/src/proto/vim9expr.pro b/src/proto/vim9expr.pro
index 233cfa2..f58e346 100644
--- a/src/proto/vim9expr.pro
+++ b/src/proto/vim9expr.pro
@@ -4,6 +4,7 @@
 int compile_member(int is_slice, int *keeping_dict, cctx_T *cctx);
 int compile_load_scriptvar(cctx_T *cctx, char_u *name, char_u *start, char_u **end);
 int compile_load(char_u **arg, char_u *end_arg, cctx_T *cctx, int is_expr, int error);
+int compile_arguments(char_u **arg, cctx_T *cctx, int *argcount, ca_special_T special_fn);
 char_u *to_name_end(char_u *arg, int use_namespace);
 char_u *to_name_const_end(char_u *arg);
 int get_lambda_tv_and_compile(char_u **arg, typval_T *rettv, int types_optional, evalarg_T *evalarg);