main.xtradb_mrr fails sporadically

main.xtradb_mrr 'xtradb'                 [ fail ]

        Test ended at 2016-03-21 20:01:27

CURRENT_TEST: main.xtradb_mrr

--- /private/var/lib/buildslave/maria-slave/labrador/build/mysql-test/r/xtradb_mrr.result	2016-03-18 07:40:58.000000000 +0200

+++ /private/var/lib/buildslave/maria-slave/labrador/build/mysql-test/r/xtradb_mrr.reject	2016-03-21 20:01:27.000000000 +0200

@@ -313,7 +313,7 @@

 explain

 select count(length(a) + length(filler)) from t2 where a>='a-1000-a' and a <'a-1001-a';

 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

-1	SIMPLE	t2	range	a	a	9	NULL	99	Using index condition; Rowid-ordered scan

+1	SIMPLE	t2	ALL	a	NULL	NULL	NULL	482	Using where

 select count(length(a) + length(filler)) from t2 where a>='a-1000-a' and a <'a-1001-a';

 count(length(a) + length(filler))

 100

mysqltest: Result length mismatch