This chapter interrogates the ‘solidarity turn’ (i.e. the increased prevalence of 'solidarity' in international legal discourse or practice) and the extent to which it truly marks a break from the ideas and practices that have characterized the neoliberal age which have shaped the international legal order and arguably led to an aggravation of the very crises solidarity is now called upon to tackle. It does so by using one of the oldest legal expressions of solidarity in international law, namely the law of collective security (CS), exploring its connections to neoliberal ideas. My argument is: (a) that neoliberals made the institutionalization of the market order the only means of securing peace; (b) that they envisaged CS as a system of international policing designed to spread and secure the international market; (c) that this neoliberal vision of CS played a role in shaping the duty of solidarity in the international law of CS; and (d) that existing critiques do not provide us with sufficient tools to challenge neoliberal (market) solidarity. The conclusion sounds a note of warning to the enthusiasm that has surrounded the adoption of solidarity in international law and calls for a renewed engagement with its ideological and material underpinnings.