Validation is a key task of any preservation workflow and often JHOVE is the first tool of choice for characterizing and validating common file formats. Due to the tool’s maturity and high adoption, decisions if a file is indeed fit for long-term availability are often made based on JHOVE output. But can we trust a tool simply based on its wide adoption and maturity by age? How does JHOVE determine the validity and well-formedness of a file? Does a module really support all versions of a file format family? How much of the file formats’ standards do we need to know and understand in order to interpret the output correctly? Are there options to verify JHOVE-based decisions within preservation workflows? While the software has been a long-standing favourite within the digital curation domain for many years, a recent look at JHOVE as a vital decision supporting tool is currently missing. This paper presents a practice report which aims to close this gap.