(Image credit: Valve)

Team Fortress 2's in-game economy went haywire last week when a bug showered players with rare, Unusual quality hats. Valve fixed the bug the following day and trade-locked the affected hats, stopping anyone profiting from the glitch—but it's now relented, and says players can trade one of the hats they obtained via the bug.

The hats came from older item crates: for a short window, opening one such crate guaranteed you an Unusual hat, which are the most sought-after items in TF2. On investigation, Valve said that a "small number of accounts acquired these hats, and a smaller portion of those accounts acquired an exceedingly large number of them" in the aftermath.

It has ruled that players can trade the first bugged hat added to their account. The rest will be permanently trade-locked. If you have more than one, you can refund the cost of the hats, or the crates or keys you got them from. Refunds will go live in "about a week", Valve said yesterday. The number of hats made tradeable represents roughly a month's worth of Unusuals.

Some players actually deleted the hats because they were worried they'd done something wrong by opening a bugged crate, Valve said. "While we appreciate the concern, you didn't do anything wrong, so hats from bugged crates deleted before the tradable date will be restored to your accounts with the same restrictions described above.

"We apologize for the inconvenience of this incident, and we’ve added safeguards to prevent incidents like this in the future," it added.