Despite curatorial diligence, low levels of annotation errors, including the transitive inheritance of author mistakes extracted from papers, inevitably creep into the bioactivity databases we have used as sources. As an operating principle P&D fixes any unequivocal errors we spot. At the same time, we notify the originating sources about these errors that could otherwise persist and proliferate between databases. However, we have found the speed with which these get fixed at source has been variable (although this is clearly dependent on build cycle times and release versions).