Hi, There was a question on the list before on prepending to the numberpart of a caption with the 'numberstarter' command, which works just fine ( https://mailman.ntg.nl/pipermail/ntg-context/2017/089142.html). I wanted to try the same but for prepending to the entire prefix (not just the number part) when prefixsegments are used, however using 'prefixstarter' does not seem to make a difference. For the sake of the example I have added the numberstarter in as well, just for comparison. Caption with the example reads "Figure 1.S.1" whereas I was expecting "Figure C.1.S.1". MWE: \setupfloatcaption[figure][number=yes,way=bytext,prefix=yes,prefixstarter={C.},numberstarter={S.}] \starttext \startchapter[title={Cow}] \startplacefigure[title={Custom caption}] \externalfigure[cow] \stopplacefigure \stopchapter \stoptext Not sure whether prefixstarter is the intended command to use, but the wiki of setupcation (https://wiki.contextgarden.net/Command/setupcaption) says it inherits from setupcounter which has both numberstarter and prefixstarter defined in the same way. Adam