Setting a fixed routeValue in .NET Core's CreatedAtAction/CreatedAtRoute

I have a Web API that allows basic CRUD using GET/POST/PUT, but also contains subobjects that are accessed through /apipath/MyObject/{objectId}/SubObject/{subObjectId}

Adding a subObject uses this method

    [HttpPost]
    [Route("{id}/Members")]
    [Produces(typeof(TeamMember))]
    public IActionResult AddTeamMember(Guid id, [FromBody] TeamMember teamMember)
    { 
      //some processing here.
      return CreatedAtAction(nameof(GetMember), new { id, memberId = teamMember.Id }, teamMember);
    }

The GetMember method looks like this

    [HttpGet]
    [Route("{id}/Members/{memberId}")]
    public IActionResult GetMember(Guid id, Guid memberId)
    { //processing here
    }

Calling CreatedAtAction in AddTeamMember throws a

'System.InvalidOperationException': No route matches the supplied values.

If I change the Route tag of GetMember to exclude the Members part, it works. So, how do I tell CreatedAtAction that there's supposed to be a Members in between id and memberId?