President Trump has spent months exhorting Republican lawmakers to send him a tax-cut bill in time for Christmas—a $1.5 trillion stocking-stuffer for businesses and families. And on Wednesday afternoon, Congress delivered, as the House approved final passage of the GOP’s top legislative priority.

But despite Trump’s impatience for tax cuts, he might not actually sign the landmark bill into law right away, White House advisers said. In fact, Trump might wait until the new year, pushing the outer boundary of the 10 days the Constitution gives the president to affix his signature to legislation passed by Congress.

The reason for the possible delay involves a complicated bit of legislative gamesmanship. Under a 2010 law requiring Congress to offset any new spending or lower taxes, the $1.5 trillion bill would trigger automatic cuts to Medicare and other programs—across-the-board reductions that Republicans don’t want to be responsible for letting take effect. By waiting until the calendar turns to 2018 to formally enact the tax bill, Trump would push the automatic spending cuts to 2019 and buy Congress another year to waive them.