A temperature-dependent switch has a first and a second stationary counter contact and a temperature-dependent switching mechanism with a contact member. The switching mechanism, in its first switching position, presses the contact member against the first counter contact and, in this case, produces an electrically conducting connection between the two counter contacts via the contact member. The switching mechanism, in its second switching position, holds the contact member at a spacing from the first counter contact. A closing lock is provided, which prevents the switch, once opened, from closing again. The closing lock locks the temperature-dependent switching mechanism permanently in the second switching position thereof in a mechanical manner.