A method, computer apparatus and computer program product for bytecode weaving is described herein. The method includes determining when a code module such as an OSGi bundle that requires bytecode weaving becomes available for loading into a system. Code associated with the code module is loaded. This code may be part of the module itself or part of a separate entity, such as an OSGI bundle fragment, but does not require weaving. Responsive to loading the code associated with the code module, a reference is received to the entity responsible for loading the code associated with the code module. A code entity (which does require weaving) within the code module is identified and a woven set of bytes are provided to the code loading entity identified via the returned reference. Consequently, the woven set of bytes represents a transformed version of the identified code entity.