A competition-best score of 76 from Dan Hodgson couldn't prevent Yorkshire slipping to a 36-run defeat against Gloucestershire in a rain-shortened match at Bristol.
Hodgson hit two sixes and nine fours in his 55-ball knock but the Vikings were dismissed for 193 in reply to the home side's imposing 229-6 in 27 overs.
Teenage off-spinner Miles Hammond finished with 2-29 in only his third senior appearance but it was seamer David Payne who was the pick of the Gloucestershire attack, taking 4-44.
Adam Lyth (27) was his first victim while he also ended Richard Pyrah's fun after the all-rounder had belted two sixes and the same number of fours in a breezy 34 towards the end of proceedings.
Gloucestershire's challenging total had been set up by their opening pair of Hamish Marshall (27) and Michael Klinger, the home skipper making 45 before departing to leave the score at 110-2.
Chris Dent proved he is fully fit after a recent back injury by making 56, including four fours and four sixes, in a high-octane innings that spanned only 40 balls.
He eventually fell to a Liam Plunkett full toss and although Alex Gidman followed soon after before he'd troubled the scorers, Benny Howell and Ian Cockbain continued the charge in the closing overs.
Howell made 32 from 22 balls, eventually becoming one of three wickets for Yorkshire paceman Iain Wardlaw, while Cockbain ended up unbeaten on 46.