After threatening to stall out several times in development limbo, the Queen biopic Bohemian Rhapsody looks like it's finally shifting into gear — and continuing to build a cast around star Rami Malek, who's set to play late singer Freddie Mercury.

The Hollywood Reporter brings word that Lucy Boynton, whose recent credits include an appearance in the similarly music-driven John Carney coming-of-age romance Sing Street, has signed on to portray Mary Austin, who lived with Mercury for years and remained a close lifelong friend after the end of their romantic relationship.

Boynton, who can also be seen in this weekend's limited release Rebel in the Rye and the upcoming Murder on the Orient Express remake, rounds out a cast that's grown fairly quickly since Malek agreed to play Mercury. As previously reported, Gwilym Lee (The Tourist) is on board to play guitarist Brian May, Ben Hardy (X-Men: Apocalypse) will star as drummer Roger Taylor and Joe Mazello (The Social Network) will appear as bassist John Deacon.

As THR's report notes, Austin was a major figure in Mercury's life — not just in terms of the lengthy friendship they maintained after their breakup, but as an acknowledged muse early in Queen's career, inspiring songs such as "Love of My Life," from 1975's A Night at the Opera.

It's unknown to what extent their relationship will be a focus of the film, but fans will find out soon enough: Bohemian Rhapsody, which is being directed by Bryan Singer from a script by Justin Haythe, is due to arrive in theaters Dec. 25, 2018. In the meantime, take a look at the first official photo of Malek in character.

Everything You Need to Know About the Queen Movie 'Bohemian Rhapsody'