Feruloyl esterases hydrolyse phenolic groups involved in the cross-linking of arabinoxylan to other polymeric structures. This is important for open-ing the cell wall structure making material more accessible to glycoside hydrolases. Here we describe the crystal structure of inactive S133A mutant of type-A feruloyl esterase fromAspergillus niger(AnFaeA) in complex with a feruloylated trisaccharide substrate.