A growing number of surgical patients present to the operating room with implantable cardioverter defibrillators (ICD). Peri-operative care of these patients dictates that ICD function be suspended for many surgical procedures to avoid inappropriate, and possibly harmful, ICD therapy triggered by electromagnetic interference (EMI). An alternative to reprogramming the ICD is the use of a magnet to temporarily suspend its function. However, this approach is not without complications. We report a case where magnet use failed to inhibit ICD sensing of EMI, and a shock was delivered to the patient. Measures to decrease EMI, controversies regarding magnet use, and expert recommendations are discussed.