Woeful West Ham defending handed Crystal Palace a point in a 1-1 draw at the London Stadium.
The Hammers were leading through a fine goal from Ghana winger Mohammed Kudus and heading for a fifth straight win in all competitions.
But West Ham’s Greek defender Konstantinos Mavropanos came bearing a gift when his crazy back-pass let Odsonne Edouard in to equalise.
Once again the Hammers’ inability to keep a clean sheet cost them – they have managed just one in the Premier League this season.
Palace looked there for the taking, especially without the attacking threat of Eberechi Eze, who suffered an ankle injury last week.
But they went close to opening the scoring when Joachim Andersen headed Michael Olise’s free-kick back across goal and Edouard volleyed wide.
However, the Hammers took the lead with their first real chance after 13 minutes.
Kudus started the move when he spun away from Will Hughes in the centre circle and found Lucas Paqueta.
The Brazilian fed the ball to James Ward-Prowse, who switched the play out to Vladimir Coufal on the right.
Czech full-back Coufal pulled the ball back for Kudus, who had continued his run into the area and thumped a first-time shot past Palace keeper Sam Johnstone.
Jarrod Bowen, back in West Ham’s attack after missing two games with a knee knock picked up on England duty, could have doubled the lead when he latched onto Nayef Aguerd’s ball over the top but his attempted lob did not beat Johnstone.
Palace went close to an equaliser before half-time when Andersen’s free-kick was deflected off the back of Edson Alvarez and looped narrowly wide with home keeper Alphonse Areola stranded.
Kudus had the ball in the net again moments after the break but Tomas Soucek was offside and interfering with play when he swung a boot at the ball.
Edouard was denied by a Ward-Prowse header underneath the crossbar as he tried to get his head onto Marc Guehi’s cross, but moments later came Mavropanos’ brain fade.
The former Arsenal defender, only in the team as Kurt Zouma was missing due to a family issue, sent a no-look back-pass straight into the path of Edouard.
The French striker could not believe his luck as he strolled forward, evaded Alvarez’s last-ditch tackle and fired low into the bottom corner.
Bowen could have won it in stoppage time, and continued West Ham’s recent run of last-gasp winners, but planted his header straight at Johnstone.