Wrong room version warnings on Element Web

For some reason Element Web sometimes opens the room version upgrade dialog when joining a room. I can reproduce this by making a Conduit user invite another Conduit user to a DM over federation. When the user accepts the invite, the room version upgrade dialog is shown. We also saw this dialog when joining public rooms over federation without invites.

The reason seems to be that Element Web can't find the room create event, but afaict it's in the state of the first /sync that contains the new room.