Urban policy directives have recently emerged within the European Union which position smart urban development as a transformative approach for delivering sustainability. This paper questions the transformative credentials of smartness and argues that it is better understood as a partial fix for the economic, environmental and social challenges faced by cities. Drawing on the urban sustainability and smart city literatures we develop the concept of the smart-sustainability fix. This concept focuses analytical attention on how smart-sustainable city initiatives work to selectively integrate environmental goals and the agendas of digital technology advocates into entrepreneurial forms of urban governance. We then explore and illustrate how smart-sustainability fixes are being constructed, in three cities, as part of a flagship European Commission initiative (Triangulum). Our research reveals three forms of fix: (1) a spatial fix - the development of smart-sustainable districts; (2) a digital fix - the digitisation of urban infrastructure to reveal hidden processes; and, (3) a collaborative fix - collaborative experimentation with low carbon and digital technologies. At the heart of these fixes lies a desire to make the urban realm more manageable. The wider application of these fixes across Europe would amplify the dominant ecological modernisation agenda of sustainable development.