diff --git a/src/evalfunc.c b/src/evalfunc.c
index 04967ef..12f7a88 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -11489,7 +11489,7 @@
 								|| flg == NULL)
 	rettv->vval.v_string = NULL;
     else
-	rettv->vval.v_string = do_string_sub(str, pat, sub, expr, flg);
+	rettv->vval.v_string = do_string_sub(str, STRLEN(str), pat, sub, expr, flg, NULL);
 }
 
 /*