The present invention relates to a safety device for securing a machine having a sensor that is configured to detect the presence of an object in a monitored zone and to output a detection signal when an object is located in the monitored zone and having an evaluation unit that is configured to receive the detection signal from the senor and to generate an output signal in dependence on the detection signal. Provision is made in accordance with the invention that the evaluation unit is adapted furthermore to generate the output signal in dependence on at least one additional criterion.