A method for extending supported voice markup. The method can include a step of identifying a reference implementation (RI) for a software component that interprets voice-based markup. The RI can define a manner that the software component interprets voice-based markup. At least one plug-in can be identified that contains an extension to the RI. At runtime, the RI can be dynamically modified in accordance with the at least one plug-in. The software component can interpret voice-based markup documents based upon the modified reference implementation.