Stricter derivative margin requirements have increased the demand for liquid collateral, but euro area investment funds, which use derivatives extensively, have been reducing their liquid asset holdings. Using transaction-by-transaction derivatives data, we assess whether the current levels of funds' holdings of cash and other highly liquid assets would be adequate to meet funds' liquidity needs to cover variation margin calls on derivatives under a range of stress scenarios. The estimates indicate that between 13 percent and 33 percent of euro area funds with sizeable derivatives exposures may not have sufficient liquidity buffers to meet the calls under adverse market shocks. As a result, they are likely to redeem money market fund (MMF) shares, procyclically sell assets, and draw on credit lines, thus amplifying the market dynamics under such stress scenarios. Our findings highlight the importance of further work to assess the potential role of macroprudential policies for nonbanks, particularly regarding liquidity risk in funds.