Infrastructure investments, a core element of slum upgrading, play a role in improving the livelihoods of over 1 billion slum residents globally. Established planning practices often successfully deliver functional infrastructure but evidence shows that their contribution to improved livelihoods often either is absent or declines sharply after some time. To explain this limited effectiveness, this article identifies the missing link between infrastructure delivery and livelihood improvements as lying in the appropriation process, that is, the uptake and embedding of infrastructures into the daily practices of residents. Recent insights from sociotechnical transitions studies help to conceptualise appropriation. The authors use Munyaka informal settlement in Eldoret town, Kenya as a case to investigate the mechanisms of new infrastructure uptake. Findings indicate that appropriation is a social process that proceeds in three steps: reception, domestication and institutionalisation. This process is driven by the need to maintain or adjust residents' livelihood practices relative to prevailing socioeconomic and spatiotemporal conditions. The study concludes that appropriation is a significant process that planners should try to anticipate. Prevalent approaches to participation have to be modified accordingly. This is essential for planning to improve livelihoods in slums.