Looks like Lily Allen and David Harbour are headed down the aisle.

Engagement rumours are swirling around the couple thanks to a selfie from the “Smile” singer.

While showing off her abs, Allen posed in workout gear and a hand on her hip but despite her killer physique, eyes were immediately drawn to the diamond sparkler on that finger.

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Allen’s Instagram followers quickly noticed the rock and asked her about it in the comment section of her post. To the questions about the ring, Allen seemingly confirmed the news, writing, “First rule of engagement club…”

RELATED: Lily Allen & David Harbour Have Fans Wondering If They Are Secretly Married

The response is in reference to the iconic “Fight Club” quote, “The first rule of Fight Club is: You do not talk about Fight Club.”

Before her relationship with the “Stranger Things” star, Allen was married to Sam Cooper. The former couple shares two daughters Marnie Rose and Ethel.

Harbour and Allen went public with their relationship in September.

ET Canada has reached out to their reps for comment.

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