diff --git a/src/proto/userfunc.pro b/src/proto/userfunc.pro
index 6ed79ba..340ef57 100644
--- a/src/proto/userfunc.pro
+++ b/src/proto/userfunc.pro
@@ -4,6 +4,7 @@
 int get_function_args(char_u **argp, char_u endchar, garray_T *newargs, garray_T *argtypes, int *varargs, garray_T *default_args, int skip, exarg_T *eap, char_u **line_to_free);
 char_u *get_lambda_name(void);
 int get_lambda_tv(char_u **arg, typval_T *rettv, int evaluate);
+char_u *register_cfunc(cfunc_T cb, cfunc_free_T free_cb, void *state);
 char_u *deref_func_name(char_u *name, int *lenp, partial_T **partialp, int no_autoload);
 void emsg_funcname(char *ermsg, char_u *name);
 int get_func_tv(char_u *name, int len, typval_T *rettv, char_u **arg, funcexe_T *funcexe);