It is crucial that patent offices grant protection only to those inventions that are novel and non-obvious. In 2004, the European Patent Office (EPO) made the unique move to systematically extend its prior art database by including documents shared among members of standard-setting organisations, but not made available to the general audience. This paper investigates the effects of this policy change. We find that it worked thanks to a significant reduction in granting rates rather than reducing the scope of granted patents. Our study demonstrates how a targeted approach can improve the quality of the patent granting process.