Duplicate keys in "collations" object with JSON response format

After upgrading Solr 6.3 -> 6.5 I've noticed a change in how json response writer outputs "collations" response key when spellchecking is enabled (wt=json&json.nl=arrarr)

Solr 6.3:

"collations":
[
["collation",

{ "collationQuery":"the", "hits":48, "maxScore":"30.282", "misspellingsAndCorrections": [ ["thea","the"]]}

],
["collation",

{ "collationQuery":"tea", "hits":3, "maxScore":"2.936", "misspellingsAndCorrections": [ ["thea","tea"]]}

],
...

Solr 6.5:

"collations":{
"collation":

{ "collationQuery":"the", "hits":43, "misspellingsAndCorrections": [ ["thea","the"]]}

,
"collation":

{ "collationQuery":"tea", "hits":3, "misspellingsAndCorrections": [ ["thea","tea"]]}

,
...

Solr 6.5 outputs object instead of an array, and it has duplicate keys which is not valid for JSON format.

Any help is appreciated.