On his way out the door, then-Speaker Boehner did his best to “clean up the barn” for incoming Speaker Paul Ryan. Notably, he negotiated a budget deal with President Obama that, among other things, raised the top-line budget number for the FY 2016 appropriations process. The deal represented a compromise between Republican defense hawks who insisted on higher national security spending and Democrats who wanted higher domestic spending. The package passed the House 266 to 167 and the Senate 64 to 35. President Obama signed it yesterday. On Sunday, Speaker Ryan told FOX News that he wants to transform the GOP from an “oppositional” party into a “propositional” party. With the “barn” clean, the general view is that he can now move on to bigger things.

But not so fast. Yes, the deal settled the overall spending level, but which, if any, new policy riders will be added to the appropriations bills? And how the overall spending allocation gets carved up and distributed among agencies and programs may get caught in the crossfire. . These are hard and controversial decisions, and Congress only has three legislative weeks to make them.

If Congress can’t come to an agreement, a government shut-down is entirely possible after the December 11 deadline—unless Speaker Ryan is willing to violate the so-called “Hastert Rule.” (Former Speaker Hastert sought to only move bills that most Republicans could support, and Speaker Ryan has indicated that he would like to do the same.)

And there’s the rub. How many House Republicans will be willing to vote for appropriations bills that omit any new riders? Will a majority of House Republicans vote for a bill fully funding Planned Parenthood? Or continuing Homeland Security grants to sanctuary cities? Or letting stand Obama regulations restricting hydraulic fracturing and coal mining, subjecting community banks to Dodd-Frank regulations, or new net neutrality rules? This seems unlikely. Republicans ranging from the House Freedom Caucus to the more mainstream House Republican Study Committee will have difficulty getting to “aye.”

Realizing this dynamic, Speaker Ryan may well craft a bill that includes all of the above riders and more. However, such a bill will never get 60 votes in the Senate— the number needed to overcome a Democratic filibuster. It might not even get a majority. In such a scenario, Republicans will be faced with a choice: let the government shut down or negotiate a new bill that can garner 60 Senate votes and the President’s signature. Achieving that, however, might require violating the Hastert Rule.

And there’s more. Earlier this year, the House had passed just six of the twelve annual appropriations bills when the potential for a vote on the Confederate flag stopped all forward movement. That issue (a proposal to ban the flag, and thereby the Mississippi state flag which incorporates it, from federal property) is still out there. Republicans have been loath to vote on (for or against) a Confederate flag amendment, but Democrats could insist on some version of it, raising the issue again and creating a potent negotiating chit for the Democrats.

Then there’s Senate Majority Leader McConnell’s vow not to let the government shut down. Of course, he may not be able to prevent a shut-down if the House refuses to act on a Senate-passed funding bill, but it will focus all eyes on Speaker Ryan. The deep internal rifts plaguing the Republican Party will again be on display.

The budget deal settled one important question—the top-line spending number—but left a slew of contentious issues unresolved. Before Christmas, expect plenty of fireworks.