diff --git a/src/proto/vim9class.pro b/src/proto/vim9class.pro
index f2e642e..e36c7e2 100644
--- a/src/proto/vim9class.pro
+++ b/src/proto/vim9class.pro
@@ -16,6 +16,7 @@
 int object_method_idx(class_T *cl, char_u *name, size_t namelen);
 ufunc_T *object_method_lookup(class_T *cl, char_u *name, size_t namelen, int *idx);
 ocmember_T *member_lookup(class_T *cl, vartype_T v_type, char_u *name, size_t namelen, int *idx);
+void emsg_var_cl_define(char *msg, char_u *name, size_t len, class_T *cl);
 ufunc_T *method_lookup(class_T *cl, vartype_T v_type, char_u *name, size_t namelen, int *idx);
 int inside_class(cctx_T *cctx_arg, class_T *cl);
 void copy_object(typval_T *from, typval_T *to);