A temperature-dependent switch which comprises a first and a second stationary counter contact and a temperature-dependent switching mechanism having a current transfer member. The switching mechanism, depending on its temperature, either closes the switch by pressing the current transfer member against the first and the second counter contact and thereby establishing an electrically conductive connection between the two counter contacts via the current transfer member, or opens the switch by keeping the current transfer member at a distance from the first and the second counter contact and thereby interrupting the electrically conductive connection. A closing lock is provided, which keeps the switch open when it has been opened for the first time. The closing lock comprises a spring washer which directly interacts with the current transfer member and mechanically locks the latter permanently when the switch has been opened for the first time so that the switch remains permanently open.