Cheltenham defeated Forest Green 2-1 to move above their Gloucestershire rivals in the League Two table.
The third-placed Robins took an early lead through Will Boyle's header from a long Ben Tozer throw-in after 11 minutes.
It was nearly 2-0 in the 22nd minute when Reuben Reid crossed for Andy Williams, who was denied by a fine reaction save from Luke McGee.
Forest Green improved as the half wore on and Jamille Matt's header was kept out by Josh Griffiths after a cross from Scott Wagstaff.
Ebou Adams' effort was off target at the end of a slick attack from the away side.
But Cheltenham doubled their lead in the 57th minute when Alfie May released Williams and he calmly converted his fifth goal of the campaign.
Forest Green restored hope when Wagstaff was brought down in the box by ex-Rovers midfielder Chris Clements and substitute Aaron Collins converted from the spot in the 73rd minute.
But Cheltenham held on for their first win over Forest Green since 1998.