Unexpected compilation error with "one value" and AnyVal classes

[plokhotnyuk]

Reporting on behalf of @kyri-petrou from his messages in the Gitter chat.

The following snippets of code fails to compile.

case class Obj(l: Map[String, String])

object Obj {
  implicit val codec: JsonValueCodec[Obj] = JsonCodecMaker.make(
    CodecMakerConfig.withInlineOneValueClasses(true)
  )
}

case class Obj(l: Map[String, String]) extends AnyVal

implicit val codec: JsonValueCodec[Obj] = JsonCodecMaker.make

The compilation error is the same:

[error]      |Exception occurred while executing macro expansion.
[error]      |java.lang.Exception: Expr cast exception: x
[error]      |of type: x
[error]      |did not conform to type: scala.collection.Map[java.lang.String, java.lang.String]