The president likes to say he’s accomplished quite a bit in his first six months. He’s signed more than three dozen executive orders, announced the U.S. withdrawal from the Paris climate agreement, and turned the White House into a reality show where someone goes home every week. But a lot of these actions don’t translate into tangible accomplishments. Technically, the U.S. is still party to the Paris accord. And most of Trump’s executive orders start the process of undoing regulations, instead of actually undoing them.

One of the few immediately effective things Trump has done, though, was approve the Keystone XL pipeline. In early January, Trump reversed the Obama administration’s 2015 rejection of the controversial 1,179-mile project that would have transported heavy tar sands oil from Canada to the Gulf Coast. There were still a few hurdles the pipeline developer had to jump through after Trump’s approval, but ultimately, his issuance of a presidential permit was seen as the last real obstacle to construction. “Keystone is a done deal,” Vermont Law School Professor Patrick Parenteau told me in April.

But Keystone XL is no longer a done deal. According to a report in The Hill, pipeline developer TransCanada is telling investors it hasn’t decided whether to build the pipeline at all. The company is unsure there are enough oil companies that would pay to use the pipeline, because tar sands oil—a heavy, high-polluting Canadian product—is becoming too expensive to extract and process. “Frankly, in the current price climate, [Keystone XL] is probably not going to be a going venture unless there’s a massive improvement in technology” for processing tar sands, University of Wyoming professor of petroleum Charles Mason told ABC News on Thursday.

Keystone XL’s potential failure would be a blow to Trump’s legacy, since approving the pipeline was one of his signature campaign promises. But it’s also a warning for Trump’s entire energy agenda of promoting dirty fuels like tar sands and coal. If the market for high-polluting fuels is in decline, then so are Trump’s policies.

