Cambridge scored twice from the spot to end League Two’s last remaining unbeaten record with a 2-0 win at Walsall.
Paul Mullin, the country’s leading scorer, slotted home his 11th goal of the season early on and, after he was taken off, Joe Ironside assumed spot-kick duties to seal the points.
Mullin stroked home his fourth penalty in as many games after Luke Hannant’s dart into the box was ended by a Liam Kinsella clip in just the ninth minute.
He could have had a second but headed Leon Davies’ cross over before Walsall keeper Liam Roberts made a superb flying save to tip over Hannant’s rising drive.
The visitors’ dominance continued after the break, Roberts producing a fine fingertip stop to prevent Mullin finding the bottom corner from 18 yards.
But Ironside secured the points for the second-placed Us on 80 minutes, sending Roberts the wrong way after Hayden White handled Kyle Knoyle’s cross.
Walsall, after six draws in their first eight games, failed to produce an effort of note as a 13-game undefeated run dating back to last season ended tamely.
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