An optoelectronic safety sensor (10) for safeguarding a machine (34), the sensor (10) comprising a light receiver (24) for optical detection of object data and a control and evaluation unit (26) configured to use the object data to decide whether a safety-critical object (36) is detected in a vicinity of the machine (34) and in this case to trigger a safety-related reaction, and wherein the control and evaluation unit (26) is further configured to adapt the sensitivity of a criterion for deciding whether a safety-critical object (36) is detected as a function of at least one of previously detected objects and simultaneously detected objects.