TransCanada Corporation’s Keystone Pipeline leaked at least 210,000 gallons of oil in an agricultural area of South Dakota Thursday morning, according to the company. The leak, which amounts to 5,000 barrels, comes just days before a last-ditch effort to halt the long-planned and highly controversial Keystone XL Pipeline expansion.

According to a press release from TransCanada, the leak was “completely isolated within 15 minutes,” but the spill puts it among the worst pipeline-related oil spills in recent memory.

The spill comes at a highly inconvenient time for TransCanada: Next week, The Nebraska Public Service Commission is set to announce a decision on the routing of the Keystone XL pipeline through the state. This is largely considered to be the last major regulatory hurdle before construction of the expansion, which former NASA climate chief James Hansen once called “the fuse to the biggest carbon bomb on the planet.”

The Keystone XL extension would serve a similar purpose as Phase 1 of the Keystone Pipeline, which pumps oil south into the United States from Canada’s tar sands. The extension has long been a political football—the pipeline was blocked by the Senate in 2014; a bill approving the pipeline’s construction passed Congress in 2015 but was vetoed by President Obama.

With the election of Donald Trump, the pipeline project was revived. (Canadian Prime Minister Justin Trudeau also expressed his support.) Yearly carbon emissions for the pipeline have been estimated to be more than 100 million tons per year.

Read More: Controversial Keystone XL Pipeline Comes Back to Life With News of Trump Win

Protesters and activists have fought hard against pipeline extensions in recent years and won two important victories during the Obama presidency. The administration came out firmly against Keystone XL and, after months of protests by indigenous people and water protectors in South Dakota, blocked the Dakota Access Pipeline in 2016.

Those victories were short-lived, as President Trump has noted that he “think[s] it's a lot safer to have pipelines than to use other forms of transportation for [oil].” Trump gutted the Environmental Protection Agency, and has largely been hospitable to oil and fossil fuel interests.

We don’t know yet whether Thursday’s spill will postpone the construction of the Keystone XL, but it is at least worth noting that an incident like this will do nothing to assuage the fears of anyone who cares about the planet.

TransCanada did not immediately respond to a Motherboard request for comment.