Dundalk 1 Derry City 0
Dundalk keeper Peter Cherrie saved a penalty to keep a fourth successive clean sheet as Derry came away from Oriel Park empty handed.
Cherrie got down comfortably to save Gareth McGlynn's 16th minute spot kick after Michael Hector had pulled down the Derry winger.
Cherrie made two further stops to deprive Eamon Zayed either side of Ruaidhri Higgins rattling the home side's crossbar.
Central defender Colin Hawkins then got what would prove the game's only goal two minutes before the break when heading home Dean Bennett's cross.