Dynamically compiled computer program code containing virtual calls can reduce the options for optimization during compilation. A virtual call can affect sections of the program code that are compiled subsequent to the virtual call. Therefore, the state under which the effected sections are to be executed may not be known at the time of compilation thus complicating optimization of these sections. If assumptions are made about the state of an effected section, then this section can be optimized. In order to provide proper operation of the executing program code given the optimization, a check of the validity of the assumptions is performed prior to execution of the optimized section. If an assumption does not hold true then the original un-optimized section can be executed to reduce adverse program performance.