Jordan Bowery fired a stoppage-time winner as Crewe ended a run of five consecutive defeats with a 1-0 win over Stevenage.
Boro's three-game winning run came to an agonising end and they were made to pay for Matt Godden's first-half penalty miss.
Crewe wasted good chances early on with Chris Dagnall shooting straight at goalkeeper Joe Fryer after a misplaced pass put him in the clear and George Cooper slicing horribly wide after Dagnall laid the ball on.
Godden spurned the chance to put Stevenage ahead in the 28th minute after he was tripped by Zoumana Bakayogo after bursting into the box. The forward fired his spot-kick straight at Crewe goalkeeper Dave Richards.
After the break neither side could find any real quality in the final third.
But with time running out, Bowery turned inside the box and fired the winner in the fourth minute of added time.