You might not expect fossil fuel companies to pay for a conference designed to shrink their industry. But in Paris, that’s precisely what’s happening.

This week and next, roughly 40,000 diplomats, activists, policy experts, and journalists are gathering in the French capital for a round of high-stakes negotiations aimed at slowing climate change. They’re packed into a regional airport that, as described by our Climate Desk partners at the New Republic, has been converted to resemble a cross between the United Nations headquarters building, Disney World’s Epcot Center, and a natural history museum.

For two weeks, all these people need to be fed, housed, transported, entertained, and equipped with space to work. Unsurprisingly, it’s an expensive undertaking—budgeted by the French government at nearly $200 million, according to EurActiv France. About one-fifth of that tab is being picked up by private corporations.

Big international conferences frequently have corporate sponsors, but given the basic aim of the Paris talks—to dramatically reduce man-made greenhouse gas emissions—some of the event’s sponsors are drawing criticism for their close ties to the fossil fuel industry. In other words, some of the companies paying to keep the lights on and the coffee flowing at the vital climate summit may have a vested interest in limiting the scope of the international agreement.

The event (known as COP21, short for 21st Conference of the Parties to the UN Framework Convention on Climate Change) has more than 50 corporate sponsors. They include the likes of Google, 3M, Puma, and IKEA. In exchange for providing the conference organizers an undisclosed sum of money, corporate sponsors get their logo splashed across high-profile surfaces—from billboards to banners to handouts—and priority access to spaces to hold branded events. Corporate participants can also get direct access to top-tier diplomats. At last year’s COP in Peru, for example, a lobbying group representing a handful of fossil fuel companies—including Shell and Chevron—hosted more than a dozen events, including one featuring UN climate chief Christiana Figueres.