split with find doesn't work if chunk has only 1 document

db.adminCommand({ enableSharding: 'test' });

db.adminCommand({ shardCollection: 'test.user', key: { x: 1 }});

db.adminCommand({ split: 'test.user', middle: { x: 0 }})

db.adminCommand({ split: 'test.user', middle: { x: 100 }})

db.user.insert({ x: 1 })

db.adminCommand({ split: 'test.user', find: { x: 1 }})

{ "cause" : { }, "ok" : 0, "errmsg" : "split failed" }