Lowly Dumbarton upset leaders Morton 3-0 to end the Ton's unbeaten run stretching back to November 10.
Quickfire first-half strikes from Garry Fleming and Scott Agnew and a third from Bryan Prunty secured back-to-back victories for Dumbarton.
The champions-elect started the brighter with Dumbarton goalkeeper Jamie Ewings twice called into action to deal with Scott Taggart's drilled shot before saving the follow-up effort from Peter Weatherson.
Those saves proved pivotal as the visitors broke the deadlock through Fleming, the midfielder taking Mark Gilhaney's pass to find the bottom corner of the net after 32 minutes.
Seven minutes later it was two as Agnew directed James Lister's cross past Morton goalkeeper Derek Gaston.
The points were wrapped up 11 minutes from time after Prunty slotted home from 12 yards.