Wayne Rooney booked a dream FA Cup reunion with Manchester United after Derby cruised past Northampton.
The striker scored from the spot to cap the Rams' 4-2 fourth-round replay win over the Cobblers on Tuesday.
They will now host 12-time winners United in the fifth round next month.
Andre Wisdom's first goal in almost eight years and strikes from Duane Holmes and Jack Marriott helped send the hosts through.
Nicky Adams' goal threatened to haul Northampton, the lowest ranked team left in the competition, back into the tie while Sam Hoskins scored a late penalty.
Rooney, the Red Devils' record scorer, returned to English football this season after 18 months with DC United.
He will now face United next month for the third time since leaving Old Trafford for Everton in 2017.
It was ultimately a routine win for Phillip Cocu's side at Pride Park following their 0-0 draw in the first tie last month.
Chris Lines and Marriott traded half chances before Derby took control and should have opened the scoring after 20 minutes.
Rooney's fine pass set Marriott away and before the striker was crowded out he slipped in Martin.
The striker looked certain to score after wrong-footing David Cornell but Michael Harriman's last-ditch tackle kept the Sky Bet League Two Cobblers level.
Cornell foiled Marriott soon after but the hosts finally opened the scoring after 28 minutes.
Rooney's near-post corner was headed into the air by Lines and, when Cornell failed to punch clear, Wisdom hooked in from close range.
It was the defender's first goal since he scored on his Liverpool debut against Young Boys in the Europa League in September 2012.
Seven minutes later it was 2-0 when Scott Malone's inch-perfect pass allowed Holmes to run clear and find the bottom corner.
But less then 90 seconds after the re-start the visitors pulled a goal back, Adams converting Paul Anderson's cross from close range.
Any nerves were eased just four minutes later, though, as the Rams restored their two-goal advantage.
Holmes broke and found Martin to stand up a cross for Marriott whose header just beat Cornell before Malone made sure.
Marriott then twice went close but Rooney wrapped up victory in the 77th minute.
Tom Lawrence was fouled by Scott Wharton in the box and the former England skipper buried a low penalty.
Northampton still had time for a spot kick of their own when Andy Williams was fouled by Curtis Davies and Hoskins – who also forced Kelle Roos into a fine late save – made it 4-2 with six minutes left.
