diff --git a/src/userfunc.c b/src/userfunc.c
index 7536234..e44397d 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -5503,6 +5503,47 @@
     ga_clear_strings(&lines_to_free);
 }
 
+    int
+get_func_arity(char_u *name, int *required, int *optional, int *varargs)
+{
+    ufunc_T	*ufunc = NULL;
+    int		argcount = 0;
+    int		min_argcount = 0;
+    int		idx;
+
+    idx = find_internal_func(name);
+    if (idx >= 0)
+    {
+	internal_func_get_argcount(idx, &argcount, &min_argcount);
+	*varargs = FALSE;
+    }
+    else
+    {
+	char_u	fname_buf[FLEN_FIXED + 1];
+	char_u	*tofree = NULL;
+	funcerror_T error = FCERR_NONE;
+	char_u	*fname;
+
+	// May need to translate <SNR>123_ to K_SNR.
+	fname = fname_trans_sid(name, fname_buf, &tofree, &error);
+	if (error == FCERR_NONE)
+	    ufunc = find_func(fname, FALSE);
+	vim_free(tofree);
+
+	if (ufunc == NULL)
+	    return FAIL;
+
+	argcount = ufunc->uf_args.ga_len;
+	min_argcount = ufunc->uf_args.ga_len - ufunc->uf_def_args.ga_len;
+	*varargs = has_varargs(ufunc);
+    }
+
+    *required = min_argcount;
+    *optional = argcount - min_argcount;
+
+    return OK;
+}
+
 /*
  * Find a function by name, including "<lambda>123".
  * Check for "profile" and "debug" arguments and set"compile_type".