This paper demonstrates a Fault Attack on anAES core protected by an infection type countermeasure. The redundant AES is implemented on a Xilinx Spartan-6FPGA, with a feature size of 45 nm. By injecting exactlythe same fault in both state registers of the redundantimplementation using lasers, we are able to annul theprotection added by the countermeasure and thus performa successful Differential Fault Analysis. This requires ahigh precision double laser setup in order to hit twodifferent locations on the chip at the same point intime. With a priori knowledge about the location of bothstate registers, we were able to generate applicable faultyciphertexts within minutes. Our results show that forapplications demanding a high level of security, relyingon a duplication of hardware is not sufficient.