The popular language-learning app Duolingo is adding courses for one of the most famous made-up languages of all time: Star Trek’s Klingon, via Engadget. The new course has been in progress on Duolingo’s “Incubator” site for the last couple of years, and it has now finally launched on the web version of Duolingo (with iOS and Android availability coming later).

The language was first invented by Marc Okrand for use in the Star Trek films and TV shows, although Okrand would later go on to develop it into a full, working language. The Duolingo course was created by a team of volunteers fluent in the constructed language, although it is officially licensed by CBS.

There were apparently a few oddities of the Klingon language that needed to be figured out before it could come to Duolingo, though. As Michaela Kron, Duolingo’s senior PR manager, notes in an interview with Engadget, “Klingon uses apostrophes in the middle of words, which is not something our system was able to handle at first, since no other language does it.” The company also had to compensate for the fact that capitalization is important in written Klingon, where meanings of words can shift depending on which letters are capitalized.

Klingon isn’t Duolingo’s first foray into adding constructed languages from popular TV shows, either: the app previously added a course for Game of Thrones’ High Valyrian last year.