Transition projects have been implemented for Flemish agriculture since 2003, but these did not enable a transformation of the agricultural sector. This paper looks at pre-transition scenarios that have been collectively designed by stakeholders of the agricultural sector in2002. These foresaw decreases in the regional animal stocks in Flanders. However, the real evolution of the sector did not reveal such a decrease. It is assumed that the individual adaptive behaviour of farmers can explain the unexpected stability of the Flemish agricultural sector. A detailed agent-based model has been built to replicate the past evolution, accounting for structural diversity of farmers, heterogeneity in behaviour, and natural resource constraints. The results indicate that different forms of rigidity in the individual behaviour of farmers slow down the adaptation of the agricultural sector. Future transition scenarios should account for these elements in order not to overestimate the speed of change in the sector. ; This project was financed by the Impuls-project of the Transnational University Limburg (TUL, Belgium and the Netherlands). A prior version of the results was presented in September 2014 at the 10th annual meeting of the European Social Simulation Association (ESSA) in Barcelona; the remarks from participants improved this manuscript. The computational resources and services in support of this study were provided by the Hercules Foundation and the Flemish Government–department EWI. Prof. Steven Van Passel thanks DG Agriculture (European Commission) for access to the Farm Accountancy Data Network (FADN). All remaining errors are the sole responsibility of the authors.