Slick Query jsonb - cannot be cast to slick.ast.OptionType

Question

I'm trying to build a query that returns a few selected columns using slick-pg for as my slick driver but I'm having issues trying to map on the json column MyValueObject. The error I am getting at runtime is...

A client error occurred: slick.driver.JdbcTypesComponent$MappedJdbcType$$anon$1 cannot be cast to slick.ast.OptionType"

My case case clase, table mapper, and query looks similar to this...

case class MyAggregateObject(foo: String, valueObj: Option[MyJsonObject)
case class MyJsonObject(bar: Int, baz: Option[String] = None)

implicit val jsonObjectMapper = MappedColumnType.base[Option[MyJsonObject], JsValue](s => Json.toJson(s),str => Json.fromJson[MyJsonObject](str).asOpt)

val q = for {
  list <- myAggregateObjects
} yield (
  list.foo,
  list.MyJsonObject.flatMap(_.baz.bind)) // throws the error!

The only solution I can come up with right now is to map on the result but the returning rows can be very large and I'd like to avoid loading a sequence of large objects into memory.