ALMA images show that axisymmetric dust rings are a ubiquitous feature of protoplanetary disks. These rings are likely caused by gas pressure bumps that concentrate solid particles. The resulting overdensity of dust may trigger planetesimal formation by the streaming instability (SI). In this talk I will present the first 3D simulations of planetesimal formation in the presence of a pressure bump modeled after ALMA observations. We use a large simulation domain with the bump in the center and a realistic dust/gas ratio of Z=0.01. We find that, for cm-size particles, even a small pressure bump produces enough particle concentration to trigger planetesimal formation by the SI; a bump does not need to fully stop particle drift or form a particle trap for the SI to be efficient and converting a large fraction of the solid content into planetesimals. For mm-size particles we find tentative evidence that planetesimal formation may not occur, but additional work with higher resolution is needed. Ultimately, however, our results suggest that for cm-sized particles, planetesimal formation in pressure bumps is an extremely robust process.