This paper investigates the adaptation of an open-source planning support system (PSS) for use in Stockholm County, Sweden. The aim of this adaptation is to make the PSS more easily useable for local planners, and thereby to help overcome the barriers (involving tool acceptance and instrument quality) preventing more widespread adoption of PSSs by planning authorities. This adaptation results in a PSS which produces up-to-date outputs and has additional functionality to make the PSS more useable for planners in the region. The adaptation is conducted with inputs from the local planning authorities to facilitate the adaptation work and allow the planners to better understand and trust the PSS. Our post-hoc review of the adaptation with the users shows that some barriers to PSS adoption in practice have been overcome, although further work and further evaluation are needed before planners are likely to frequently operate the PSS themselves.