This paper analyzes the cost of disinflations under real wage rigidities in a micro-founded New Keynesian model. The conventional view is that real wage rigidities can be a useful mechanism to generate a slump in output after a credible disinflationary policy because they prevent the immediate adjustment of inflation. This view is flawed, since it depends on analyzing the model in a linearized framework. Once nonlinearities are taken into account, the results change both qualitatively and quantitatively. Disinflations actually lead to a permanently higher level of output, and real wage rigidities increase the output during the adjustment to the new steady state.