A self-resetting circuit is simulated in a switch-level simulator using simulation models that can conditionally treat an unknown value on an input node as a known value. An attribute is included with the simulation model. The attribute specifies to the simulator whether to treat an unknown value as a logical zero or a logical one. A single attribute can be associated with the simulation model, or one attribute can be associated with each input node. Self-resetting circuits can be simulated from an initial state that includes unknown states. The proper logical initialization behavior can be simulated while still allowing the self-resetting circuit to propagate unknown states during normal operation and simulation.