Llantwit Major's long unbeaten run in the Cymru South ended with a 3-0 defeat at Taffs Well.
Ben Stait's side had not lost in league action since August and were aiming to stretch their undefeated streak to ten matches.
But their hosts at Rhiw Dda'r - currently second bottom in the table - were out to cause a Friday night upset against their near neighbours.
The Wellmen went ahead after nine minutes from a superb free kick which was turned in by Drew Banner, who went onto make it a brace soon after the half hour mark.
Major showed some positive signs towards half time as they looked to find a way back, roared on by a vocal Windmill Army.
But their hopes were dashed on 57 minutes when a defensive error allowed Sam Johnson to round keeper Jack Lansdown and bag a third for the hosts.
Llantwit remain fifth in the table as most of the league enters takes a fortnight's break due to the Welsh Cup.
Next up is the second leg of Major's Fenix Trophy first round clash against Berchem Sport on Wednesday, with the Belgian club leading 7-2.
Tickets are still on sale for the return leg at the STM Glass Stadium in Bridgend, with the club urging fans to buy in advance. Kick off is at 7.30pm.
JD Cymru South results
Afan Lido 4-1 Cwmbran Celtic
Ammanford 0-2 Caerau Ely
Baglan Dragons 2-2 Newport City (Saturday)
Cambrian United 0-1 Trethomas Bluebirds (Saturday)
Carmarthen Town 0-1 Pontypridd United (Saturday)
Goytre United 1-3 Trefelin BGC
Llanelli Town 3-0 Penrhiwceiber Rangers
Taffs Well 3-0 Llantwit Major
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