In the debate on ‘flexicurity’, relatively little attention has been paid to how responsive traditional areas of social security have been to increasing flexibility in the labour market. This article tries to fill this gap by focusing on the Belgian pension system. In particular, it asks to what extent pension regulation in the three pillars has been adapted to the proliferation of atypical forms of employment. It does so by examining whether there are significant differences between old age protection of standard and non-standard workers. The article pursues a double research strategy: an analysis of Belgian legislation and relevant collective labour agreements is complemented with a statistical analysis of the Panel Study of Belgian Households (PSBH). The results show that part-time employment results in a lower first-pillar pension, while other forms of temporal flexibility such as career interruptions and temporary unemployment do not. In the second pillar, our findings suggest that workers with contractual flexibility and job mobility are discriminated against. Finally, non-standard workers do not appear to compensate for lower pension protection through increased participation in the third pension pillar. Our findings suggest the need for a re-assessment of the system of ‘assimilated’ periods. To conclude, we point to some implications for the design of flexicurity policies.