A banknote validator (1) comprises: a housing (5, 6); a validation sensor means (13); and a banknote drive mechanism (9); wherein the banknote drive mechanism (9) is arranged to transport a banknote from an input aperture (3) to a stacking means, said banknote drive mechanism (9) delimiting a first banknote pathway (17) proximal to the input aperture (3), and a second banknote pathway (18) proximal to the stacking means; characterised by a pivotable security gate arrangement (22) that is resiliently biased to project into the second banknote pathway (18).