Katy Perry Rocks Out to Kanye West's 'Famous' Taylor Swift Diss -- Watch!

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It's Katy Perry's party and she can throw shade if she wants to.

The "Rise" singer appeared to do just that on Tuesday, as she celebrated her 32nd birthday jamming out to Kanye West at his concert at the Forum in Inglewood, California -- and filmed her hilarious reaction to his "Famous" line dissing Taylor Swift.

WATCH: Katy Perry Celebrates Her Birthday By Voting for Hillary Clinton and Moshing at Kanye West's Concert

While Perry may just happen to be a big fan of Swift's other nemesis, something tells us her reaction to the infamous line isn't a coincidence.

Watch below: 

WATCH: Katy Perry to Co-Chair the 2017 Met Gala Following Taylor Swift

Interestingly enough, Perry and Swift -- and their mutual ex, John Mayer -- attended the same birthday party earlier this week. The singers both hit up Drake's 30th birthday soiree at Delilah restaurant in West Hollywood, California.

See more in the video below.