Short-sellers were rubbing their hands as CFD group Plus500 Limited (LON:PLUS) shed more than a third of its value on a warning results this year would be far below previous expectations.
PLUS500 was one of the most shorted shares on the London stock market ahead of the update.
Tighter European regulation on CFD trading had affected revenues more than expected said the Israeli group.
Combined with increased marketing to attract customers this had hit profits, which would be 'materially lower than current market expectations' as a result.
Plus500 also reduced its final dividend payout by 24% having boosted the interim by almost six-fold.
Profits for the year rose 90% to US$379mln but were boosted by an exceptionally strong first quarter when cryptocurrency trading was feverish.
Asaf Elimelech, chief executive said the business had seen a marked reduction in group revenue directly attributable to the new regulatory framework.