NEGINFIF function with "-Inf" returns error on 4.6, 5.0

Someone in the Couchbase Gitter channel was querying why the following N1QL where clause works in 4.5 and no longer does in 4.6+
"WHERE expires_at > NEGINFIF($time, "-inf")"

The error they receive on 4.6+ is
"Error evaluating scanCount(). - cause: json: unsupported value: +Inf from xxx:9101 - cause: json: unsupported value: +Inf from xxx:9101"

They updated their query to the following, but want to know why the previous query stopped:
"WHERE expires_at > IFNULL($time, false)"

Also, is there a correct way to deal with Infinity? eg is there a keyword that can be used?