Google’s mobile app store maintains a monopoly in the market for distribution of programs and payments on its Android software, a federal jury in California decided, dealing a blow to the technology giant in a high-stakes antitrust battle with Epic Games Inc.

The internet giant’s Play store willfully wields monopoly power through the Alphabet Inc. unit’s anticompetitive conduct, jurors found Monday after deliberating for less than four hours following a nearly monthlong trial in San Francisco. The ruling could potentially jeopardize billions of dollars of revenue generated by Google’s app store. Two years ago Epic largely lost a similar antitrust challenge to Apple over its app store.