A method for executing a machine code based on a dynamic language is disclosed. An execution guard is created as a value stored in a data structure. The value is representative of an expected condition or a set of conditions for a reusable portion of the machine code. The value representative of the expected condition(s) is compared to an actual value encountered later during execution of a portion of the machine code. The reusable machine code is executed if the actual value corresponds with the value representative of the expected condition(s). The execution guard is invalidated if any of the expected conditions changes.