The invention relates to a pump assembly (1) for supplying negative pressure to a pneumatic brake booster, wherein the pump assembly has at least two elastic displacement elements (2, 2') which are moved by connecting rods (3, 3'), said connecting rods (3, 3') each being rotatably mounted on an eccentric element (4, 4'). The eccentric element (4, 4') has a bearing seat element (5, 5') and a force element (6, 6'). At least two eccentric elements (4, 4') are secured next to each other on a drive shaft (7) that rotates about an axis of rotation (R), and interlocking anti-rotation means are provided that determine a defined angular position of the eccentric elements (4, 4') relative to each other about the axis of rotation (R). In order to improve the ease of assembly and simplify the manufacturability, the invention proposes that the anti-rotation means are designed as shaped elements of the bearing seat element (5, 5') in such a way that they engage in each other in an interlocking manner when the eccentric elements (4, 4') are in a defined angular position relative to each other.