Method, apparatus and product for using traces of an original model to verify a modified model. The method comprising obtaining a trace exemplifying a checker failing in a model; obtaining a modified model, wherein the modified model is a modified version of the model which was modified in an attempt to resolve the checker failing in the model; re-simulating the trace in the modified model to generate a second trace, wherein said re-simulating is performed by a processor; comparing the trace and the second trace to identify a common prefix, wherein the common prefix ends immediately before a cycle in which a state according to the trace is different than a state according to the second trace; and guiding verification of the modified model using values derived from the common prefix.