On their own, House Democrats can’t do much to guard against the unprecedented opportunities for presidential corruption created by Donald Trump’s vast global business empire. On Thursday, they asked congressional Republicans to help them out.

Rep. Elijah Cummings and 21 other Democrats in the House released a letter urging Speaker Paul Ryan to join their demand for the president-elect to turn over “all documents” about his overseas business assets. Specifically, they’re calling for the disclosure of Trump’s personal and corporate tax returns, which thus far he’s refused to release, as well as all income statements from companies Trump owns “in whole or in part”:

As Cummings’s letter notes, Trump’s personal finances stand to benefit from foreign businesses and governments seeking favor with the White House. Foreign diplomats have already admitted to spending at Trump-owned businesses to impress the president — something independent ethics experts say will likely run afoul of the Constitution’s emolument clause if it continues once Trump is sworn in.

On Monday, Sen. Elizabeth Warren and House Democrats introduced separate legislation to force Trump to divest entirely from his foreign business holdings. The letter Cummings released on Thursday has a more limited request: that the president-elect simply make public the extent of his business holdings.

For now, there’s little reason to believe that Speaker Ryan will be eager to go along. Ryan’s has publicly expressed confidence that Trump will distance himself from his business assets before taking office, but hasn’t called on Trump to take specific action or endorsed Democrats’ legislation forcing him to do so.

“I have every bit of confidence [Trump is] going to get himself right with moving from being the business guy that he is to the president he’s going to become,” Ryan said in December 2016, according to Politico.

Judging by Trump’s new plan to avoid conflicts of interest — which Vox’s Libby Nelson called “a sham” — Ryan’s faith looks like it may be misplaced.

Read the letter from House Democrats in full here.