After The New York Times dropped a bombshell report this week that Donald Trump may not have paid taxes for 18 years because of a $916 million real-estate loss, Trump’s central defense is that he simply obeyed applicable laws and paid what he was required to pay, and no more. “As a businessman and real estate developer, I have legally used the tax laws to my benefit, and to the benefit of my company and my employees,” Trump told a crowd in Colorado on Monday. “It is these politicians who wrote the tax code, and who are constantly adding, revising, and changing, an already over-complicated set of laws—all at the behest of their favored donors and special interests.”

Trump is right on both counts: There’s no evidence he broke the law, and the tax code does indeed have a fantastic number of special industry carve-outs. Few industries have received more exemptions and treats from the tax system than the real-estate industry, which has spent hundreds of millions of dollars aggressively lobbying Congress for special treatment.

Trump claimed Monday that “fixing the tax code is one of the main reasons I’m running for president,” but his actual tax plans say nothing about real-estate exemptions, and is heavily focused on providing even more advantages to wealthy individuals and corporations.

If Trump is looking for ideas, Senator Bernie Sanders helpfully announced this week he will provide some. Sanders plans to introduce a bill in the new Congress next year that will address some of the very loopholes that allow people in the real-estate industry to take such great advantage of the tax code.

While the bill hasn’t been fully written yet, Sanders’s office outlined four areas the bill plans to address. Some are loopholes we know Trump used, others are ones he could have used in his long real estate career. (The only way to know for sure would be for Trump to release his tax returns.)

Sanders’s bill will directly address “passive loss” tax laws that exempt the real-estate industry. When Ronald Reagan signed a tax-code overhaul in 1986, taxpayers were barred from using losses from businesses they were not directly involved with to offset actively earned income—but there are huge carve-outs for real-estate losses. Sanders would eliminate those carve-outs.

The bill would also end special exemptions that allow people in the real-estate industry to claim losses beyond what they are actually liable for—these laws would allow Trump to write off losses on a project beyond what he really invested. The bill would also change how capital-gains taxes are calculated on real-estate sales, as well as change industry-friendly debt and depreciation rules.

Both President Obama and House Republicans have introduced tax plans that would, in different ways, end some special tax treatment of the real-estate industry. Each time, the bills are met with ferocious lobbying campaigns. The real-estate industry spent $95 million on federal lobbying in 2014 alone, which is triple what it spent in 1998. So Sanders’s bill will no doubt face stiff resistance.

But there is a more immediate political utility—Sanders is trying to puncture Trump’s populist credentials by calling attention to these tax breaks and Trump’s failure, so far, to outline any proposed changes. Sanders is also using this political moment to underscore the long-held progressive desire to change the priorities of the US tax code.

“In one day, Donald Trump did more than I have done in a year to show how corrupt the political system is, how rigged the tax system is,” Sanders told a crowd in Dearborn, Michigan, this week. “He boasts how rich he is, how much he has, and does not pay a nickel in federal income taxes.”

When he announced his looming legislation, Sanders said, “Special tax breaks and loopholes in a corrupt tax code enable billionaires and powerful corporations to avoid paying their fair share of taxes while sticking the burden on the middle class.”

He continued: “It’s time to create a tax system which is fair and which asks the wealthy and powerful to start paying their fair share of taxes.”