(Bloomberg) -- On the day that Rolls-Royce Holdings Plc shares surged to a near six-year high on a boost to the jet-engine maker’s cash pile, the stock’s most bearish analyst has called an end to its dizzying gains.

“We are surprised to see the shares up so much in today’s trading,” said Berenberg’s Philip Buller, the only analyst with an outright sell rating, among 21 banks surveyed by Bloomberg. “Given the run in the shares and lack of obvious positive catalysts in the next six months or so, it’s hard to see why the enthusiasm for this crowded trade doesn’t wane in the weeks ahead.”

Rolls-Royce shares have almost quadrupled since the end of 2022 as the firm’s earnings benefit from a post-pandemic surge in demand for long-haul aircraft engines. It’s the best-performing stock on the entire Stoxx Europe 600 Index over the past 12 months.

The stock is valued at 19 times earnings expected two years from now, meaning there is no longer a discount to France’s Safran — a maker of engines in the higher-growth market for short-haul narrowbody planes, according to Buller.

“Rolls deserves a discount,” he said. “You simply cannot ever generate the same return on investment in wide over narrow.”

The shares extended their gains on Thursday, rising as much as 12%, after Rolls reported higher-than-expected earnings and gave strong profit and cash flow forecasts.

While the guidance pleased most analysts, Buller said investors he had spoken to had hoped the firm would have finally announced a resumption of dividend payments, which were canceled during the outbreak of Covid-19.

Berenberg’s price target of 240 pence is the lowest among analysts and implies about 34% downside over the next 12 months. At its current 355 pence, the stock has already met the average price target and has become technically overbought based on an index of relative strength.

Read more: Rolls Royce CEO Promises More Growth as Long-Haul Travel Surges

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