Compile failed on case class with default value and type parameter

[liewhite]

case class Z[T](
    a: T,
    b: Long = 1
)
@main def main = {
  println(generateDocs(deriveConfig[Z[Int]]).toTable.toGithubFlavouredMarkdown)
}

Compile error:
Exception occurred while executing macro expansion.
java.lang.Exception: Expected an expression. This is a partially applied Term. Try eta-expanding the term first.