The Vijolicasti lost home and away to npower Championship side Birmingham in last season's competition yet took the lead three minutes from half-time when Robert Beric prodded home.
Former Swansea midfielder Sigurdsson has yet to find his feet since his summer arrival, but went some way to repaying the north Londoners' faith by lashing home to ensure his side did not leave the Stadion Ljudski vrt empty-handed.
Source: PA
Source: PA