diff --git a/src/regexp.c b/src/regexp.c
index 8e6e9c4..1bd1261 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -1817,14 +1817,14 @@
  * call_func() by vim_regsub_both().
  */
     static int
-fill_submatch_list(int argc UNUSED, typval_T *argv, int argskip, int argcount)
+fill_submatch_list(int argc UNUSED, typval_T *argv, int argskip, ufunc_T *fp)
 {
     listitem_T	*li;
     int		i;
     char_u	*s;
     typval_T	*listarg = argv + argskip;
 
-    if (argcount == argskip)
+    if (!fp->uf_varargs && fp->uf_args.ga_len <= argskip)
 	// called function doesn't take a submatches argument
 	return argskip;