Microsoft Corp. (NASDAQ:MSFT) is suing Samsung Electronics Co. Ltd. (KS:005930) over unpaid patent payments from last year.

On Friday, Microsoft claimed that the South Korean electronics giant failed to honor its agreement to pay royalties for using the Android operating system for its smartphones after Microsoft announced plans to acquire part of Nokia’s (HE:NOK1V) business last fall.

“Unfortunately, even partners sometimes disagree,” Microsoft deputy general counsel David Howard wrote in a Friday blog post.

Microsoft typically requires any companies using the Google (NASDAQ:GOOG) Android operating system to pay patent royalties.

Other electronics companies such as LG (KS:066570) and HTC (TW:2498) have all agreed to pay, but Motorola, which has been in a legal battle with Microsoft since 2010, has not, according to a Reuters report.

Microsoft made such an agreement with Samsung in 2011. Within three years, its smartphone sales quadrupled, according to IDC.

When Microsoft announced plans to buy Nokia’s handset business in 2013, Samsung said it was breaching their contract, and refused to pay fees.

“After becoming the leading player in the worldwide smartphone market, Samsung decided late last year to stop complying with its agreement with Microsoft,” Howard wrote, adding that Samsung used Microsoft’s 2013 acquisition of Nokia’s handset business as a breach of contract, according to the lawsuit, which was filed in the Southern District of New York.