Can't join a room with room membership access over federation

[GearKite]

Trying to join a room with access set to space members over federation results in: MatrixError: [403] Answer from example.com: [403 / M_FORBIDDEN] M_FORBIDDEN: Event is not authorized.

Steps to reproduce:

1. Create a space
2. Create a room under that space with Visible to space members
3. Invite a user on another homeserver to the space
4. Attempt to join the room from the other homeserver

Doing this with 2 accounts on a single homeserver seems to work fine.