A circuit for detecting a fault injection in an integrated circuit including: at least one logic block for performing a logic function of said integrated circuit; an isolation block coupled to receive a signal to be processed and an isolation enable signal indicating a functional phase and a detection phase of the logic block, the isolation block applying, during the functional phase, the signal to be processed to at least one input of the logic block, and during the detection phase, a constant value to the input of the logic block; and a detection block adapted to monitor, during the detection phase, the state of the output signal of the logic block, and to generate an alert signal in case of any change in the state of the output signal.