A hearing aid having an input transducer (2), a signal processor (3), an output transducer (4) and an adaptive filter (5) for generating a feedback cancellation signal (101) further comprises a norm estimator (10) generating a first norm signal (109) indicative of a norm of the electrical input signal and a second norm signal (110) indicative of a norm of a feedback-cancelled electrical input signal, a comparator for comparing the first and second norm signals and generating a difference value Nfbc−Nx and a decision unit disabling application of the feedback cancellation signal to the signal path of the hearing aid if the difference value is above a certain threshold value cth thus avoiding the feedback cancellation mechanism actually increasing acoustic feedback of the hearing aid. The invention also provides a method for reducing acoustic feedback of a hearing aid, a computer program, and an electronic circuit for a hearing aid.