We present long-baseline interferometric observations of Gaia19bld, performed with the PIONIER instrument mounted on the VLTI. Our time-series observations allow us to measure the angular Einstein ring radius to a high accuracy, as well as the direction of the source-lens relative motion. Combining our measurements with parallax measurements from ground-based photometric follow-up yields the lens mass to a high accuracy. We will explain our observing strategy, how the modeling of the interferometric data was performed, and how it was combined to photometric measurements to derive the lens mass and distance. We will also discuss the accuracy of our measurements in comparison with previous published results.