A method for operating a Coriolis mass flowmeter (1) having at least one measuring tube (2) and at least one sensor (3), wherein the sensor (3) emits an electric sensor signal depending on the temperature of the sensor (3), the sensor (3) is mechanically coupled to the rest of the Coriolis mass flowmeter (1) via a connection (5) and the connection (5) has a thermal resistance. To provide a method for operating a Coriolis mass flowmeter that makes recognition of a change in the connection possible an electric excitation signal is generated, the excitation signal is impressed in the sensor (3), the sensor signal influenced by the excitation signal is detected, a change between the detected sensor signal and a reference signal is determined and the change between the detected sensor signal and the reference signal is associated with a change in the thermal resistance.