Query works in playground but not from postman

I have created a query to pull two specific columns from a specific item. When I run the query in the playground it works as expected and I can see the results I am after in the results section. However, when I run the exact same query from Postman I get two error messages ("No such type DropdownValue, so it can’t be a fragment condition; also receive this same error for the TimeTrackingValue column). Here is the query I am running

{
  items(ids: [12345678]) {
    id
    name
    column_values(ids: ["property", "duration"]) {
      ... on DropdownValue {
        id
        text
      }
      ... on TimeTrackingValue {
        id
        started_at
        duration
        history {
          started_user_id
          started_at
          ended_at
          created_at
        }
      }
    }
  }
}

Does anyone know why the query works fine in the playground and not in Postman?