A wrinkle detector for detecting creases or wrinkles to protect a print head of a fabric printer from occlusion by protruding fabric. The wrinkle detector comprises a mounting located in advance of a print head relative to fabric approaching to be printed, the mounting comprising one or more deflectable elements extending into a predetermined clearance zone between the printing head and the fabric, wherein deflection of the elements is used as an indicator of fabric protruding into the clearance zone. The detector may be used to halt or modify printing, in particular ink jet printing of the fabrics so that occlusion does not block the printing nozzles.