In 1983, Zemco Manufacturing, Inc. (Zemco) (plaintiff) entered into a written, one-year contract to sell parts to Navistar International Transportation Corp. (Navistar) (defendant). The original contract was extended by written agreements until 1987, after which Zemco and Navistar orally agreed to extend the contracts. Navistar purchased all of its parts requirements from Zemco until 1995. Navistar then began buying parts from another company, and Zemco sued for breach of contract. Navistar argued that the oral contract extensions were unenforceable, because they violated the statute of frauds. Zemco argued that the time extensions did not need to be in writing, because they were modifications of a non-definite contract term. The district court granted summary judgment for Navistar, finding that the oral renewals of the contract did not comply with the statute of frauds.