Traders are pushing Anglo American shares above the value of BHP Group’s takeover proposal, a sign they expect a higher bid from the suitor or an interloper.

BHP’s proposal, which values the target at £31.1-billion ($38.9-billion), has several moving parts — it calls for Anglo shareholders to receive BHP shares, plus stock in two listed Anglo units that would be spun off.

Add it up and the deal values Anglo at about 2 400 pence a share, according to a rough calculation by Bloomberg News based on where all the stocks are trading near midday in London. Anglo American shares are up 13% to 2 498.00 pence, about 4% above the implied potential bid price.

While that premium isn’t huge, it’s a clear sign of traders’ expectations: Takeover targets typically trade at a discount to an offer price, even when there’s a firm proposal agreed to by both sides, to reflect the risk that a deal won’t go through, or that it will take a long time to be completed.

A quick poll of nine analysts and risk-arbitrage traders in Europe shows they expect a miner such as Rio Tinto and Glencore to step in, or BHP to boost its offer. The big prize: Anglo’s production of copper, a key metal for the energy transition, used in everything from batteries to electrical wiring.

“Given the market dynamics and the increasing demand for copper linked to the energy transition, it’s plausible to anticipate a potential ‘bump’ in interest around Anglo American’s assets,” said Gregory Lafitte, a sales analyst at Churchill Capital.

The calculation of the deal value to Anglo American shareholders doesn’t account for any dividends.

The growing demand for copper has pushed prices of the metal to a two-year high this week as investors bet that miners will struggle to service a surge in demand.

“BHP would have to offer more for this business we think mainly because it wants the copper and copper companies trade at a premium,” said Richard Hatch, an analyst at Berenberg. “BHP is going to have to pay up for it and if they do it’s going to be an expensive deal.”