The change was made due to "moderate violence" in a lightsaber fight, starship dogfights, and laser weapons, including a scene with brief "bloody detail".
The reclassification was revealed in the BBFC's 2024 annual report and applied to the film's cinema re-release last year.
Other films also saw rating changes, with A Star Is Born moving from U to 12 due to implied suicide, and US TV comedy series Fraser from PG to 12 for language and drug references.
These updates coincide with the BBFC classifying the highest number of films in its 112-year history in 2023, following new guidelines on sex scenes, violence, and drug misuse.