diff --git a/src/proto/vim9class.pro b/src/proto/vim9class.pro
index 9edf354..f2e642e 100644
--- a/src/proto/vim9class.pro
+++ b/src/proto/vim9class.pro
@@ -2,6 +2,7 @@
 int object_index_from_itf_index(class_T *itf, int is_method, int idx, class_T *cl);
 void ex_class(exarg_T *eap);
 type_T *class_member_type(class_T *cl, int is_object, char_u *name, char_u *name_end, int *member_idx);
+type_T *class_member_type_by_idx(class_T *cl, int is_object, int member_idx);
 void ex_enum(exarg_T *eap);
 void ex_type(exarg_T *eap);
 int class_object_index(char_u **arg, typval_T *rettv, evalarg_T *evalarg, int verbose);