[TxMt] Bundles showing up empty on older versions of TextMate

The latest version of my bundle was created in one of the recent higher-level builds, and I'm getting reports from users that when opening the bundle in an older version of TextMate (948) the bundle shows up completely empty.

This sounds like the result of the recent back-end changes. But I know that many of the bundles have been updated to include groups.

Assuming this is not all just some crazy bug... I guess the real question is:

Is it necessary for me to say that a particular version of a bundle *requires* a particular version of TextMate?

If so, which build of TextMate is required to run which bundle versions?

~oliver