Yeast that can referment beer poses a great risk to commercial brewers and homebrewers. Saccharomyces cerevisiae var. diastaticus is a close relative to brewer’s yeast that can excrete glucoamylase enzymes that metabolize starches. Scientific understanding of this contaminant is lacking, and better identification procedures need to be developed. In light of recent commercial recalls and with growing pressure on yeast manufactures, S. cerevisiae var. diastaticus is a timely topic of discussion for brewers at home and in the industry.