The ban is a result of a feud between the two companies over holiday shipping speed.

Amazon temporarily blocked its sellers from using FedEx Ground for their Amazon Prime shipments. According to the Wall Street Journal, the ban will remain in effect until the delivery methods employed by FedEx “improve.” Amazon already stopped using FedEx Ground for its own shipments starting in September. However, Amazon’s third-party sellers were able to continue using the service until Tuesday.

This move from Amazon comes amid the holiday season, when packages are shipped at the greatest rate of the year. Unfortunately, its also a time of year that tends to bring poor weather and driving conditions, which impair shipments. There are also fewer days to Christmas from Easter this year, which aggravates America’s shipping system further.

The partnership between FedEx and Amazon has been turning into something of a rivalry recently. When Amazon introduced one-day shipping, FedEx followed closely behind with Sunday shipping. In August, FedEx decided against renewing its contract with Amazon for shipping Amazon products aboard FedEx planes.

While FedEx benefited from Amazon’s business, both companies are doing fine on their own. Amazon’s shipping process has come a long way, while FedEx still has contracts with Walmart, Walgreens, and others.