tert alert! A thiamine diphosphate (ThDP)‐dependent enzyme catalyzing the cross‐condensation of a keto acid with several activated and nonactivated ketones gives chiral tertiary alcohols, products that are otherwise difficult to obtain in an enantioenriched form. To enable comparison of aldehyde‐/ketone‐accepting enzymes and to guide site‐directed mutagenesis studies, we solved the crystal structure