A late header from Tom Dallison saw the Valiants slip to an away loss at Colchester on Saturday afternoon.
Andy Crosby was without the services of the injured James Gibbons while Harry Charsley made his first start in midfield in place of Tom Pett.
David Worrall fired into the side netting early on, while at the other end Freddie Sears shot straight at goalkeeper Tomas Holy from close range.
Vale came close to scoring when Charsley dispossessed Dallison and advanced towards goal only to shoot straight at Shamal George. Colchester countered on the half-hour mark through veteran Sears, whose shot flashed wide.
Dallison headed in Noah Chilvers’ corner from close range in the 85th minute to earn United their first home win since November and end Vale’s nine-match unbeaten run.
After the break Worrall’s deflected shot was saved before Vale substitute Mal Benning’s cross was then pushed away from underneath his own crossbar by keeper George.
But Dallison struck to give Colchester the lead before George turned substitute Jamie Proctor’s effort away late on.
Vale: Holy; Smith, Martin, Hall; Worrall, Garrity, Charsley, Hussey (Benning); Edmondson, Cooper (Proctor), Wilson (Harratt)
Subs: Stone, Walker, Hurst, Pett