Ben Williamson struck late to break Forest Green hearts as Port Vale came through 3-2 to book their place in the second round of the FA Cup.
Williamson climbed off the bench with 18 minutes to go and hit the winner with 10 remaining after the Blue Square Premier side fought back from two goals down.
Ashley Vincent and Clayton McDonald had put the League Two side in control but James Norwood stirred Rovers into life just before the break and Eddie Oshodi leveled soon after, only for Williamson to have the final say.
Vale went ahead after seven minutes when Louis Dodds' cross-field pass found Vincent, who skipped past challenges from Ed Asafu-Adjaye and Jamie Turley to place the ball to Sam Russell's left.
The visitors doubled their lead five minutes later, Vincent turning provider, taking down Ryan Burge's cross and supplying McDonald with a close-range finish.
Forest Green were stunned but fought their way back when Norwood curled into the top corner after 34 minutes and they were level when skipper Oshodi tapped in from close range.
Rovers piled on the pressure and went close when Matty Taylor's shot was cleared off the line by McDonald but they couldn't find a winner and were made to pay when Williamson nodded home.