Prosthetic aortic valve dysfunction presenting as aortic regurgitation is a complication of mechanical valve replacement. We describe a case of late valve dysfunction caused by an annular suture of excessive length obstructing the closure mechanism of a bileaflet prosthetic valve.We present this rare cause of valve dysfunction in an 80-year-old male patient who presented with haemolysis and dyspnoea. At the time of operation it was found that a long vertically positioned annular valve suture was interfering with the normal closure mechanism of one of the prosthetic leaflets causing eccentric regurgitation jets. These findings were misdiagnosed as paravalvular leaks on the preoperative transoesophageal echo. No paravalvular leak was identified intraoperatively. After removal of the responsible suture normal prosthetic valve function was restored.Whilst early aortic valve dysfunction caused by suture material has previously been reported, this is the first report of suture material causing late dysfunction.