ColumnMetadata.cellValueType() doesn't return correct type for non-frozen collection

CREATE TABLE ks.cf (
    hash blob,
    report_id timeuuid,
    subject_ids frozen<set<int>>,
    PRIMARY KEY (hash, report_id)
) WITH CLUSTERING ORDER BY (report_id DESC);

INSERT INTO ks.cf (hash, report_id, subject_ids) VALUES (0x1213, now(), {1,2,4,5});

sstabledump mc-1-big-Data.db 
[
  {
    "partition" : {
      "key" : [ "1213" ],
      "position" : 0
    },
    "rows" : [
      {
        "type" : "row",
        "position" : 16,
        "clustering" : [ "ec01eed0-49d9-11e7-b39a-97a96f529c02" ],
        "liveness_info" : { "tstamp" : "2017-06-05T10:29:57.434856Z" },
        "cells" : [
          { "name" : "subject_ids", "value" : "" }
        ]
      }
    ]
  }
]

cqlsh:ks> select * from cf ;

 hash   | report_id                            | subject_ids
--------+--------------------------------------+-------------
 0x1213 | 02bafff0-49d9-11e7-b39a-97a96f529c02 |   {1, 2, 4}