Model-driven development (MDD) is increasingly relevant in the software development landscape. However, its adoption in the industry remains challenging. According to several studies, inadequate tool support, combined with insufficient expertise in the workforce and organisational and social factors, is part of the problem. One area for improvement in tool support is the implementation of adequate debugging mechanisms for models and systems generated from those models. This paper introduces a debugger for models specified with the SCCD (SCXML extended with class diagrams) formalism, which combines statecharts with class diagrams. The debugger, a crucial tool in the context of MDD, supports debugging models and model-generated applications from those models while always reasoning at the model level. The debugger integrates with an open-source modelling and simulation tool for the SCCD formalism. Such debugging mechanisms are a stepping stone towards wider modelling adoption