Abstract: A pump assembly for supplying negative pressure to a pneumatic brake booster, wherein the pump assembly has at least two elastic displacement elements which are moved by connecting rods, the connecting rods each being rotatably mounted on an eccentric element. The eccentric element has a bearing seat element and a force element. At least two eccentric elements are secured next to each other on a drive shaft that rotates about an axis of rotation and an interlocking anti-rotation device is provided that determines a defined angular position of the eccentric elements relative to each other about the axis of rotation. In order to improve the ease of assembly and simplify the manufacturability, the anti-rotation device is designed as shaped elements of the bearing seat element in such a way that they engage in each other in an interlocking manner when the eccentric elements are in a defined angular position relative to each other.