A circuit breaker is disclosed, in particular for low voltages, with moving and fixed contacts, a switching shaft and a contact lever. The contact lever is rotatably mounted on or in the switching shaft, and includes a free end that extends from the switching shaft, carries the contact piece of the moving contact on one side of its external contour and has a first depression on the other opposite side of the external contour for engaging a bolt. In at least one embodiment, the contact lever is subjected to a torsional moment in the closing direction by means of the bolt in each case. To ensure opening, it is proposed that a second depression be provided at a distance from the first depression, that a slot-shaped recess be formed on the switching shaft, that the contact lever, in the event of a trip, moves the bolt towards the side wall of the recess which lies in the direction of movement, which pushes the bolt out of the first depression into the second depression, the depth of which is such that the bolt lies on the bottom of the recess, which rises radially in the closing direction in such a way that a counter force must be overcome in order to rotate the contact lever in the closing direction.