Emily Blunt and Rachel Weisz have signed on to play sisters in Lynn Shelton’s new semi-improvised, and currently untitled, comedy project.

The film will be Shelton’s follow-up to the well-received bromance film Humpday, and will see her reunite with producer Steven Schardt.

Production will commence next month in Seattle and is expected to run for a month, allowing both actresses to squeeze it in to their busy schedules.

The idea of seeing Blunt and Weisz play sisters in an improvised comedy is incredible. I’m sure that with Shelton’s low-key expertise, and the commercial draw of both actresses, this film will be a sure-fire hit.

Blunt will next be seen in Universal’s sci-fi mystery The Adjustment Bureau, while Weisz portrays a Nebraskan cop in The Whistleblower. Both of which will be released early next year.

Deadline reported this one.