Shameless star Emmy Rossum is demanding a raise; and the standoff over her salary negotiations is why Showtime has thus far failed to renew the drama for an eighth season, according to The Hollywood Reporter.

Sources tell THR that Rossum wants to be paid the same amount as her co-star William H. Macy, and has even suggested that she should be paid more per episode than Macy, who has earned more than her on the show for years.

Macy, who recently renegotiated his contract and received a raise, has always earned more than his co-stars, given his film pedigree and past Oscar, Golden Globe and Emmy nominations. The last time the cast renegotiated their contracts was several years ago, and all series regulars received raises at that time. Macy's exact salary is unconfirmed, but sources tell THR that his paycheck puts him "in the upper echelon of cable dramas." Rossum plays the eldest daughter of Macy's character on the show.

Rossum also directed her first episode of Shameless this season, and her star has clearly been rising not just on the show, but publicly. And she may not have the Oscar and Emmy noms Macy does, but she was Golden Globe nominated for Phantom of the Opera, and has released multiple albums. Point being, her request isn't completely (or even remotely) out of left field.

If she successfully renegotiates her salary, then it's likely her other co-stars will renegotiate theirs as well. If Rossum can not come to an agreement with Showtime and producer Warner Bros. Television, then the network would either have to renew the show without one of its main stars, or cancel it entirely.

(Full disclosure: is owned by CBS, one of Showtime's parent companies.)