The concept of “organisational resilience” stirs real interest amongst risk management researchers. It recognises that risk control depends on the capacity of an organisation to take account of “irregular variations, disruptions and degradation of expected working conditions” (Hollnagel, Leveson and Woods, 2005, Woods 2005), or the organisation's skills in « managing the unexpected » (Weick and Sutcliff, 2001). Our paper proposes discussion of organisational resilience in the case of a project to add a new automation system to highly reliable, complex operational systems. We show that the flexibility of part of the organisation maintains the illusion of resilience. Flexibility, the capacity to improvise, redefine roles, immediately correct errors and learn from them, sharing experiences and collective anticipation (Weick & Sutcliffe, 2001) do not work for the project as a whole. They are concentrated in those areas where constraints accumulate and the divide generated by the difficult combination between the rigidity of certain elements and the flexibility of others constitute a major risk factor. A resilient organisation is not an organisation which prevents adjustments but an organisation which can identify the circulation of adjustments within it, regulate that circulation, avoid substantial imbalance and ensure that the different links of the chain are capable of dealing with them.