A device for protecting a plug-in connection between a first power plug of an electric appliance and a switchable power socket. The switchable power socket has a socket for receiving the first power plug and a second power plug for coupling the switchable power socket to an electrical mains. The device has a wall which, when the device is installed, at least partially surrounds the switchable power socket with the first power plug plugged therein. The wall is formed with a plug-side recess in which the second power plug at least partially penetrates the wall. The wall covers the first power plug at least partially, when the device is installed, in order to prevent the first power plug from being pulled out of the socket. A sensor detects whether or not the wall surrounds the switchable power socket and informs a control unit that controls the electrical device.