Evelyn Vlastos (plaintiff) owned a four-story building in Pittsburgh, Pennsylvania. Vlastos and her son operated a bar and luncheonette on the first floor of the building. An unrelated corporation operated a massage parlor on the second floor and used part of the third floor. Vlastos stored supplies and maintained an office on the fourth floor. A portion of the third floor was also used as a residence for the building’s janitor. When Vlastos obtained insurance for the building, the insurance policy included a warranty that was incorporated into the policy. This warranty, titled Endorsement No. 4, contained the following language: “Warranted that the 3rd floor is occupied as Janitor’s residence.” On April 23, 1980, a fire broke out in the building. The insurer, Sumitomo Marine & Fire Insurance Company (Sumitomo) (defendant), refused to pay the resulting insurance claim, alleging that Vlastos had breached the warranty by permitting the third floor to be used as something other than a janitor’s residence. Vlastos filed suit against Sumitomo, seeking recovery on the insurance claim. The district court ruled that the warranty in Endorsement No. 4 required the third floor to be used exclusively as a janitor’s residence. The jury found that Vlastos had breached the warranty. Vlastos appealed.