Chelsea progressed to the quarter-finals of the FA Cup courtesy of Tammy Abraham’s goal – and his clearance off the line.
The visitors were out of sorts in the first half against their Championship opponents but broke the deadlock midway through the second.
Reece James collected Billy Gilmour’s pass and darted towards the edge of the six-yard box before teeing up Abraham for a simple finish.
And Abraham preserved the lead by getting his head to Michael Sollbauer’s shot after keeper Kepa had failed to gather a free-kick.
Chelsea will be at home to Sheffield United in the next round.
They remain unbeaten under Thomas Tuchel, having won four of their five matches – and conceded just one goal – since the German took over as Blues boss.
Chelsea: Kepa, Christensen (Rudiger 45), Zouma, Alonso (James 45), Hudson-Odoi, Gilmour, Kante, Hudson-Odoi, Ziyech (Anjorin 69), Emerson, Pulisic (Kovacic 80), Abraham.
Subs not used: Caballero, Chilwell, Azpilicueta, Bate, Giroud.