The stabilization of low frequency plasma instabilities by a minimum B-field is well-known. The generation of such a field configuration is often done by adding to the main B_z-field the transverse field of Joffe bars, carrying large currents. In this letter stabilization in a minimum B-field, created by adding the field of permanent magnets to a magnetic mirror field is reported. At not too high field strengths, this is a technically very simple method to obtain a minimum B-field configuration.