An unusual complication following colonic interposition for oesophageal atresia is described, where a fistula between an aberrant right subclavian artery and the colon graft caused severe haemorrhage. As in cases of aorto-oesophageal fistulae from foreign body ingestion, we experienced a 'herald'-bleed before a second near-fatal event. In such cases, the clinical assumption should be that the source of bleeding is a major artery and appropriate resuscitation including preparations for immediate thoracotomy is required. Consideration should also be given to this potential complication when using the mediastinal route for an oesophageal replacement graft.