Hi, there is a % missing after \setupcurrentcollector: \def\pack_boxes_collector[#1][#2]% todo: keep reference point {\pack_boxes_collector_check_box{#1}% \ifconditional\c_pack_boxes_collector_valid_box - \setupcurrentcollector[#2] + \setupcurrentcollector[#2]% \expandafter\pack_boxes_collector_yes \else \expandafter\pack_boxes_collector_nop \fi} Wolfgang