S&P Global, the financial services and credit rating company, today downgraded Tether’s stability rating to its weakest level. The move targets Tether’s stablecoin, USDT, which is the largest in the cryptocurrency market, with more than $184 billion in circulation.

The rating agency cited concerns over Tether’s increased exposure to volatile assets like Bitcoin and gold in its reserves, which creates potential depegging risks for the stablecoin. S&P Global also pointed to gaps in disclosures and governance as factors in the downgrade.