I'm trying to query for a field that can be null or its _gt, but cannot find a way to make this work.

I've tried this:

  query GetBanner {
    foo(
      sort: "posicao:asc", 
      where: { 
        startDate_lt: "2021-10-13T21:13:16.510Z", 
        _or: [
          { endDate_gt: "2021-10-13T21:13:16.510Z"},
          { endDate: null }
        ]
      }
    ) {
      id
      created_at
      updated_at
      startDate
      endDate
    }
  }

But I'm getting the following error message: Invalid format, expected a timestamp or an ISO date

How to properly query this?