1. A hearing aid comprising: an input transducer transforming an acoustic input signal into an electrical input signal; a processor generating an electrical output signal by amplifying said electrical input signal according to a processor gain; an output transducer transforming said electrical output signal into an acoustic output signal; an adaptive feedback suppression filter generating a feedback cancellation signal; and a model gain estimator determining a model gain estimate of the adaptive feedback suppression filter and generating an upper limit of said processor gain, said model gain estimator including a model evaluation block providing a control parameter indicating a possible misadjustment of the model.