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Though Taraji P. Henson and Terrence Howard go way back, starring together in 2005's "Hustle and Flow," the friendship between the "Empire" co-stars has reportedly cooled.

Taraji is actually responsible for Terrence even landing the role of Lucious on the hit show in the first place: She reportedly refused to play Cookie unless Terrence was cast on the show opposite her. But it seems the actress may be regretting that ultimatum.

"She's irritated by the pompous, bigheaded braggart that Terrence has become," sources on the set of the hit Fox series shared with In Touch magazine. "In the beginning, Taraji was the key supporter and apologist for his behavior. But as his arrogance increased, she began to get annoyed."

The source went on to note that the show's stars don't hide their distaste for each other, with Taraji "staring daggers" at Terrence when they're on set together for more than 30 seconds.

Star magazine also got in on the drama: "Terrence is jealous that Taraji is getting so much airtime and will barely speak to her if the cameras aren't rolling," their source claimed.

The tension between the two may be palpable, but that isn't entirely bad news for "Empire" producers.

According to the In Touch source, producers of the series are fine with the off-camera feud, which they feel "prompts some amazing, volatile scenes between them." They claim it helps rather than hurts their on screen performances, claiming, "The animosity is working to the show's advantage."

But Gossip Cop slammed the rumors after speaking with Taraji's rep, who insisted there's no bad blood between the television stars. The rep stated that the two "are the best of friends and professional colleagues … always."