Dundee United managed to avoid a Scottish Cup shock after scraping a 1-0 win at Airdrieonians.

The Premiership bottom side had to wait until the 79th minute for the goal that saw them safely through to the fifth round.

United headed into the tie at the Excelsior Stadium without a win in their last nine matches and with boss Mixu Paatelainen admitting "a cup shock might be in the air".

However, a Blair Spittal free-kick proved to be the difference between the sides and denied League One Airdrie a replay at Tannadice.

The Diamonds quickly set about trying to take advantage of any nerves within the United ranks and could have been ahead after just three minutes.

Bryan Prunty's looping header looked set for the top corner, but goalkeeper Eiji Kawashima came to the rescue when he somehow managed to tip it over.

United soaked up the early pressure and only the woodwork prevented them from taking the lead when a fierce strike from Paul Dixon rattled the crossbar.

Spittal pounced on the rebound, but he was denied by a fine save from teenage keeper Rohan Ferguson, who was deputising for the banned Neil Parry.

The first half was fairly evenly contested and Jamie Bain fired just over for Airdrie before Chris Erskine's shot was blocked at the other end.

After a frustrating goalless first half, travelling fans must have been wondering how their side failed to open the scoring two minutes after the restart.

Scott Fraser teed up a clear shot at goal for Billy Mckay, who looked certain to leave the net bulging but somehow managed to smash his effort into the side-netting instead.

United then passed up another great chance when Dixon's cross found Fraser at the back post and he volleyed agonisingly wide of target.

With over an hour gone and still no breakthrough, the top-flight side threw new signing, Finnish striker Ruki Riski, into the action.

But it was Airdrie who threatened next when their substitute, Dylan Mackin, stung the palms of Kawashima with a shot from distance.

But it was United who still looked more likely to find the elusive opener.

And Ferguson was called into action to make another impressive save when he got down low to block a thunderous effort from Fraser.

But the rookie goalkeeper was finally beaten when United surged into the lead after 79 minutes.

Fraser was fouled just outside the box and Spittal stepped up to dispatch a lovely curling free-kick into the top corner.

The goal sparked wild scenes of celebration among the United support, with some fans spilling from the stand on to the trackside.