Leyton Orient bowed out of the FA Cup as Idris El Mizouni's unfortunate own goal proved decisive for National League leaders Chesterfield, who will visit Watford in the third round.

The match was given the go-ahead after a morning inspection, after fans helped clear the surface of snow, and Adam Thompson was included in the O's matchday squad for the first time this season at a chilly SMH Group Stadium.

Brandon Cooper came into the starting line-up in place of Dan Happe in a late change, with Darren Oldaker firing over for the hosts in the second minute.

Max Sanders found Theo Archibald with a fine diagonal pass on eight minutes, but his effort was held by Ryan Boot.

And when Archibald found Ruel Sotiriou with a fine through ball, the Cypriot U21 international's pass was just behind Shaq Forde.

The lively Sanders found Forde soon after, but the home defence were able to get back and clear, before Oldaker sent another attempt over from the edge of the box.

Sol Brynn was alert to Will Grigg's backheeled attempt from a corner on 27 minutes, while Jamie Grimes headed straight at the O's keeper from Liam Mandeville's corner.

Tom James saw his well-struck 25-yard effort held by Boot on 36 minutes, with Cooper denying Grigg from Tom Naylor's through ball moments later.

The Spireites took the lead on 39 minutes, though, when El Mizouni headed a cross over the head of Brynn and into his own net, with Sotiriou making way for Dan Agyei before the interval.

Forde and Sanders made way for Joe Pigott and Darren Pratley during the break, with El Mizouni seeing a shot deflected behind by Grimes on 54 minutes.

Pratley headed wide from the resulting corner, with Cooper booked for a foul on Grigg on the hour before Ollie Banks was cautioned for a challenge on Rob Hunt.

Ethan Galbraith and George Moncur replaced Archibald and El Mizouni midway through the second half, with Agyei firing a powerful effort at Boot on 71 minutes.

Naylor had his name taken for a foul on Agyei, before Ed Turns and Cooper had chances at a corner but could not test Boot.

And claims for a penalty, when Galbraith saw his powerful effort hit Mike Jones nine minutes from time, were turned down by the referee as O's went out.

Leyton Orient: Brynn, James, Turns, Cooper, Brown, Sotiriou (Agyei 41), Archibald (Galbraith 68), El Mizouni (Moncur 68), Forde (Pigott 46), Sanders (Pratley 46), Hunt.
Unused subs: Howes, Sweeney, Thompson.

Attendance: 8,232 (including 569 O's fans).