Cannot get query plan or status for distinct() routed through mongos

I am unable to find any way to get the query plan and stats for a distinct query in mongo shell. explain() is not valid to chain onto distinct(). The 2.2 documentation says (http://docs.mongodb.org/v2.2/reference/command/distinct/) says that "the command returns a document that contains an array of the distinct values as well as the query plan and status."

mongos> db.actions.distinct("a",

).explain is not a function (shell):1

mongos> db.runCommand({distinct:'actions', key:"a", query:{...}})