FiftyThree, makers of the popular drawing app Paper, may be gearing up for a legal battle with Facebook over its app of the same name.

On the same day Facebook announced its app last week, FiftyThree filed a trademark for the name "Paper" with the US Patent and Trademark Office.

The news comes a day after Georg Petschnigg, CEO of FiftyThree, publicly asked Facebook to change the name of its app.

"We think Facebook can apply the same degree of thought they put into the app into building a brand name of their own," Petschnigg said in a blog post where he accused the company of bullying developers. "An app about stories shouldn’t start with someone else’s story. Facebook should stop using our brand name."

Though the trademark just appeared in the USPTO's online database Tuesday, the application is dated Jan. 30, 2014, the same day Facebook officially announced its standalone newsreader Paper.

It's not yet clear whether FiftyThree would move forward with any legal claims against Facebook, though the trademark application is certainly a sign the company is doing everything it can to protect its name.

Petschnigg said Facebook apologized to FiftyThree for not alerting them of the app's name sooner but stopped short of offering a solution. Facebook has not publicly commented on FiftyThree's trademark or Petschnigg's letter.

FiftyThree's drawing app Paper has been in the App Store since 2012 when it was named the iPad app of the year. The startup raised $15 million in funding in 2013.

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