returning array from N1QL JS function fails

create function firstElem(a) language javascript as { "math", "firstElem" }

create function restArr(a) language javascript as { "math", "restArr" }

select firstElem([0, "foo", true]), restArr([0, "foo", true])

{

    "code": 5010,

    "msg": "Error evaluating projection. - cause: Error executing function restArr (math:restArr): json: cannot unmarshal array into Go value of type map[string]interface {} - cause: json: cannot unmarshal array into Go value of type map[string]interface {}"

  }