So far, it has not been possible to identify a general sequence motif for O-glycosylation in bacteria. In this issue, Charbonneau et al. demonstrate why O-glycosylation is mediated by a 13-residue strand-loop-strand motif which is part of a 19-residue imperfect repeat in the passenger domain of bacterial autotransporters. This motif provides a convenient 'glycosylation cassette' and raises intriguing questions about the structural regulation of the glycosylation pathway.