West Ham face a major test of their improvements to crowd control at the London Stadium after drawing Chelsea in the EFL Cup.
The Hammers' move to their new ground has been beset by problems, culminating in fights breaking out among supporters during the recent defeat by Watford.
The club have already relocated 200 disgruntled fans, beefed up segregation and vowed to improve stewarding but still have no police presence in the stadium due to the lack of a suitable radio system.
In their programme notes prior to the Wednesday night's third-round meeting with Accrington, co-chairmen David Gold and David Sullivan wrote that they expect the issues "to be resolved in the coming weeks".
West Ham were handed 'low-risk' early fixtures as they settled into their new home, with Bournemouth and the Hornets the first visitors and no London rivals due until Arsenal head to Stratford in December.
But Dimitri Payet's last-gasp free-kick to beat League Two Stanley means a derby against Chelsea next month and an earlier-than-expected test of the security and stewarding.
The tie will also be a stern examination on the pitch, with West Ham struggling to see off Accrington following a run of four straight defeats in all competitions.
"It's not an easy draw, of course," admitted manager Slaven Bilic. "But the one good thing about that game is that it is four or five weeks from now.
"In the meantime we're going to be totally different than before the Accrington game. We need a couple more wins. That's what we are planning to do."
The result was harsh on Accrington and especially goalkeeper Elliot Parish, who had repelled everything West Ham threw at him until France star Payet stepped up to curl the ball home in the sixth minute of stoppage time.
"It's almost heartbreaking, isn't it?" Parish told the club website. "It was such a blow to let it slip so late.
"It went through my mind that it would be a good free kick - and I'm sure a lot of goalkeepers have thought that now."