WARNING:: This article contains major spoilers for Star Wars: The Last Jedi, in theaters now.

Much of the subplot of Star Wars: The Last Jedi involves the Resistance's fuel supplies dwindling as it's doggedly pursued by the First Order, which can now track a starship through hyperspace. But how did the First Order develop this technology? The answer actually can be found in an Easter egg planted in Rogue One: A Star Wars Story.

RELATED: The Last Jedi Secured the Second-Highest Opening, Ever

Reddit user /u/rhodetolove spotted the reference in the Rogue One scene in which Jyn Erso searches for the Death Star plans. Among the Empire files is something called "hyperspace tracking." With Rogue One taking place before Star Wars: A New Hope, that means the Galactic Empire, and theoretically, the First Order, have been working to perfect hyperspace tracking for decades, before finally succeeding by the time of The Last Jedi.

Lucasfilm executive Pablo Hidalgo confirmed the Easter egg on Twitter with a simple "Ah-yup," along with a screenshot of text explaining hyperspace tracking was originally explored in a "secret Imperial think tank known as the Tarkin Initiative."

Written and directed by Rian Johnson, Star Wars: The Last Jedi stars Mark Hamill as Luke Skywalker, Daisy Ridley as Rey, John Boyega as Finn, Adam Driver as Kylo Ren, Oscar Isaac as Poe Dameron, Andy Serkis as Supreme Leader Snoke, Domhnall Gleeson as General Hux, Gwendoline Christie as Captain Phasma, Anthony Daniels as C-3PO, Lupita Nyong’o as Maz Kanata, Benicio Del Toro as ‘DJ’, Kelly Marie Tran as Rose Tico, Laura Dern as Vice Admiral Amilyn Holdo, and the late Carrie Fisher as General Leia Organa. The film is in theaters worldwide.

(via BuzzFeed)