Derby County 1 Preston North End 1
Preston, who beat the Rams over two legs at the end of last season before losing to West Ham, were heading for victory after Claude Davis scored from close range.
But former Derby defender Youl Mawene was a adjudged to have deliberately handled nine minutes from the end and Tommy Smith put away the spot-kick.
It looked a harsh decision and Preston were clearly angered by it, but Smith gratefully grasped the lifeline to stretch Derby's unbeaten run to four games.
Preston are now unbeaten in 12 and showed why they are so difficult to break down by suffocating the home side in midfield.
They had the better of the first half but there were few chances although Derby came closest to scoring when Dexter Blackstock had a header cleared off the line and Carlo Nash saved smartly from Smith.
The second period also belonged to the visitors who looked more menacing and had gone close several times before the goal came.
Chris Sedgwick had seen a header saved by Lee Camp and when the resulting corner came over Davis stabbed the ball in at full stretch from eight yards.
That looked good enough to seal victory but Derby showed plenty of spirit and got their reward with nine minutes left. Richard Jackson crossed from the left and when the ball struck Mawene's raised arm, the referee pointed to the spot and Smith sent Nash the wrong way before stroking the ball into the net.
Preston came close to regaining the lead in the last few minutes but Camp made three crucial blocks to make sure his team did not finish empty-handed.