Companies in global value chains respond to the general sustainability agenda in society by inserting sustainability clauses into their contracts and it has been argued that there is a need to develop general contract law (default contractlaw rules) in order for it to be able to respond to this sustainability agenda. This article firstly examines the basis for this view and three specific areas of interest in this regard. Secondly, it draws attention to the internal tensions that will be created in the chain by on the one hand pursuing sustainability goals, external to the interests of the contracting parties, and on the other hand a consequential need toprotect the supplier as the weaker party in the chain.