splitVector command fails on a collection with collation

  mongos> use chetan switched to db chetan mongos> db.createCollection("contacts", {collation: {locale: "fr"}}) { "ok" : 1 } mongos> db.contacts.insert({category : 1}) WriteResult({ "nInserted" : 1 }) mongos> db.contacts.insert({category : 2}) WriteResult({ "nInserted" : 1 }) mongos> db.contacts.insert({category : 3}) WriteResult({ "nInserted" : 1 }) mongos> db.contacts.insert({category : 4}) WriteResult({ "nInserted" : 1 }) mongos> db.contacts.insert({category : 5}) WriteResult({ "nInserted" : 1 }) mongos> db.runCommand({splitVector : "chetan.contacts", keyPattern : { "_id" : 1}, maxChunkSize : 256}) { "ok" : 0, "errmsg" : "couldn't find index over splitting key { _id: 1.0 }", "code" : 27, "codeName" : "IndexNotFound" } mongos> mongos> db.getCollectionInfos() [ { "name" : "contacts", "type" : "collection", "options" : { "collation" : { "locale" : "fr", "caseLevel" : false, "caseFirst" : "off", "strength" : 3, "numericOrdering" : false, "alternate" : "non-ignorable", "maxVariable" : "punct", "normalization" : false, "backwards" : false, "version" : "57.1" } }, "info" : { "readOnly" : false }, "idIndex" : { "v" : 2, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "chetan.contacts", "collation" : { "locale" : "fr", "caseLevel" : false, "caseFirst" : "off", "strength" : 3, "numericOrdering" : false, "alternate" : "non-ignorable", "maxVariable" : "punct", "normalization" : false, "backwards" : false, "version" : "57.1" } } } ]