'X-Files' star Gillian Anderson has poked fun at her co-star David Duchovny for not knowing how to tweet properly.

Duchovny tweeted earlier to wish Anderson a happy birthday, saying: "Happy Birthday, Gillian. If you see Dana, tell her Fox says she might wanna polish up the ol' badge soon-ish. Love, D".

Happy Birthday, Gillian. If you see Dana, tell her Fox says she might wanna polish up the ol' badge soon-ish. Love, D

— David Duchovny (@davidduchovny) August 9, 2016

Aside from the good wishes, the hint that the duo might be returning to our screens "soon-ish" has also got people talking.

Broadcaster Fox is said to be in "significant talks" with the show's creator Chris Carter, and its two stars, for new episodes.

'The X-Files' returned for a limited run earlier this year, to high ratings and mixed reviews.

But, possibly unbeknownst to him, Duchovny forgot to tag Anderson's Twitter handle in the birthday tweet.

However Anderson obviously saw it regardless, as she replied: "If you see @davidduchovny, tell him to tag me in his tweets. And thank you schmoopie!"

If you see @davidduchovny, tell him to tag me in his tweets. ?? And thank you schmoopie!
https://t.co/mVLFzO7Tim

— Gillian Anderson (@GillianA) August 9, 2016

The truth, and apparently a Twitter user guide, is out there...