We are modifying the Nova hypervisor to protect the operating system it hosts, against frequent transient faults resulting from cosmic radiations or manufacturing defects in the CPU. The method relies on the CPU internal exceptions management mechanisms, redundancy of execution and the machine check architecture. Here we will present how to deal with external interrupts, that is one of the challenges faced when it comes to execute short sequences of operating system's instructions twice. Ton erst ab Minute 3!