Lewis Macleod's incisive first-half strike gave Rangers victory against a youthful Airdrieonians and stretched their lead at the top of Scottish League One to 14 points.
With Bilel Mohsni and Jon Daly threatening the home goal with headers it had looked like a comfortable win.
But the Diamonds went close from Gregor Buchanan's overhead kick and Willie McLaren's shot, saved by Cammy Bell.
The slackness that enveloped Rangers will be a concern for their manager.
Ally McCoist will, of course, be delighted to have seen his team register their 17th win in 18 matches, their only faltering step on their expected march to the title coming in
a 1-1 Boxing Day home draw with Stranraer.
But the grumbles from the away fans signified that all was not well with this Rangers performance against the bottom side in the league.
Lee Wallace's early appetite to advance from defence at New Broomfield gave Airdrie a torrid time on their right flank.
Twice in the first half his forays set up team-mates with goalscoring opportunities, with an early cut-back for Fraser Aird setting the tone, though the Canadian-born player hesitated a fraction too long and had his shot blocked.
And Macleod sent a dipping shot a foot or so over the bar after Wallace's cross was headed to the edge of the box.
However, the Scotland international was not always the provider - his one-two with Nicky Law was followed by flicking the ball over Jamie Bain's head and flashing a right-foot volley just wide of Danny Rogers' goal.
Daly's ability in the air offers Rangers an attacking threat. The Diamonds had been warned when his flick-on set up Nicky Clark inside the box, though his over-stretching meant his left-foot shot lacked power.
Macleod's precise finish gave Rangers victory
But in 18 minutes Rangers took the lead, with Daly knocking Lee McCulloch's long ball on to Macleod, whose first touch took him clear of two white-shirted defenders and his second lashed the ball home.
Gary Bollan's young Airdrieonians side were never short of effort but, despite a couple of chances, never looked like registering a win against a team that had beaten them three times already this season.
Jim Lister headed straight into Rangers goalkeeper Cammy Bell's arms and Caolan McAleer got through the light blue back line with a low shot from 25 yards.
If those efforts were lightweight, two of their first-half challenges were not and were met with bookings by referee Greg Aitken.
Nathan Blockley thundered into visiting midfielder Ian Black and McAleer hit Macleod high in a rash challenge just outside the penalty box.
Mohsni headed an Aird corner over the bar with the goal gaping and Rogers saved a Daly header in 47 minutes from Aird's delivery.
Rangers enjoyed the bulk of possession for most of the second half, with Aird often the provider of balls into the box, notably for McCulloch whose header was cleared a yard from the goalline.
However, slackness began to creep into the visitors' play and too often they resorted to crosses from deep up to Daly and the longer the half wore on, the more Airdrieonians realised they could yet win a point.
Rogers rushed off his line to make a fine close-range save from Clark and Macleod volleyed wide before Airdrieonians almost levelled when Gregor Buchanan sent an overhead kick a foot wide of Bell's left-hand post.
Two corner kicks into the Rangers box added to the sense of the home side fighting back but, like the league leaders' second-half attacks, they amounted to nothing.
However, as full-time approached McLaren smashed a shot at the Rangers goal and Bell reacted smartly to divert the ball to the corner of the goal where Mohsni was well placed to clear.
While Rangers left Lanarkshire with the points, they will hope a late injury to Macleod is not serious. The midfielder pulled up sharply off the ball and had to be helped off the pitch.
And, after the final whistle, Mohsni received a second booking and a red card following an incident as the players made their way off the park.
- 01 Rogers
- 02 Gilmour
- 03 Bain Booked
- 04 Watt
- 05 O'Byrne
- 06 Buchanan
- 07 McAleer Booked
- 08 McCormack
- 09 Lister Booked
- 10 Blockley Booked (Parker - 71' Booked )
- 11 McLaren Booked
- 12 Parker
- 14 Boyle
- 15 Coult
- 16 Cadden
- 17 Grier
- 18 Coogans
- 19 Stewart
- 01 Bell
- 02 Faure
- 05 Wallace
- 08 Black Booked
- 03 Mohsni Booked
- 06 McCulloch
- 04 Aird
- 11 Law
- 09 Daly
- 07 Clark (Foster - 86' )
- 10 MacLeod (Crawford - 91' )
- 12 Foster
- 14 Crawford
- 15 Peralta
- 16 Simonsen
- 17 Shiels
- 18 Sanchez Cribari
- 19 Little
Ref: Greg Aitken