Round tripping an union type with a single string field throws an exception

[mrakgr]

open FSharp.Json

type ClientMsgs =
    | ProjectDir of string

Json.serialize (ProjectDir "qwe") |> Json.deserialize |> fun (x : ClientMsgs) -> x |> printfn "%A"

This throwing an exception surprised me. I guess I'll try adding a second field.

Edit: That works around the issue.