Casino Guichard-Perrachon SA shares fell as much as 4.8 percent after the French grocer’s debt rating was cut to junk by Standard and Poor’s, increasing interest costs as short seller Carson Block attacks its accounting.

The long-term debt rating was lowered by one step to BB+, the highest non-investment grade, Standard & Poor’s said in a statement Monday. The outlook is stable. S&P had said it may lower it as many as two levels. The company said the move will increase its financial costs by less than 20 million euros ($23 million), before tax and excluding planned bond buybacks.

The shares fell 4.2 percent to 47.27 euros as of 9 a.m in Paris. The stock had gained 20 percent in the past month as Casino reported the sale of its stake in a Thai grocer and amid speculation a unit in Vietnam could fetch more than 1 billion euros, according to John Kershaw, an analyst at Exane BNP Paribas.

“The downgrade therefore is a blow, but we expect Casino will buy-in bonds, softening the financial burden,” Kershaw wrote in a note.

Before it's here, it's on the Bloomberg Terminal. LEARN MORE