Snooker legend Jimmy White was involved in a furious row with referee Ben Williams during his Northern Ireland Open clash against Luca Brecel.
White was left livid after the official wrongly identified his object ball, triggering an awkward exchange between the duo.
The 60-year-old was 3-0 down and out of sorts when he nominated the brown ball in the fourth frame, only for Williams to mistakenly call 'blue ball'.
White tersely corrected him, which prompted the referee to amend his call and then innocently chuckle at the error.
Former UK and Masters champion White then snapped: "What's funny about that? What's funny about that?" He then appeared to raise his hand towards the official.
Williams then warned him, and when White asked why, he replied: "For sticking the finger up at me. If you do anything again, it will be a frame to your opponent."
White insisted he had not raised his finger, and the spat continued after the frame, which Brecel won to seal a comfortable 4-0 victory.
Six-time Crucible finalist White urged Williams to 'look at the video' as he continued to insist he did nothing to warrant a warning. Williams replied: "It looked like it to me." The pair did shake hands, however.
After the match, Brecel told Eurosport: "I don’t know what happened. I just heard Jimmy say ‘what’s funny about that?’ because the referee was laughing.
“I think the referee was just trying to be nice [by] laughing a bit. But Jimmy wasn’t happy.”
Ronnie O'Sullivan launched an impassioned defence of his pal and fellow pro White, insisting there was no malice in his action.
"I can see why Jimmy hasn't seen the funny side of that," he said. "He's having a hard time out there, he's not playing well. The referee has jumped the gun. There's no reason to call a colour. Whatever ball Jimmy hits is the one he's intending to hit.
"Then the referee starts laughing. Jimmy's done nothing with his hand other than, like 'what's going on?' Then he's warned him, which is just uncalled for, really."