Members of the House Freedom Caucus succeeded in modifying the budget plan GOP leaders are using to set up their party-line package to deliver on President Donald Trump’s agenda.

The House Budget Committee voted 21-16 on Thursday to adopt an amendment that would shrink the amount of tax cuts Republicans can enact if they don’t slash $2 trillion in spending at the same time. House Republican leaders negotiated the amendment with members of the group of fiscal conservatives to lock in support for clearing the budget plan through committee and bolster their chances of adopting it on the floor.

Under the budget resolution — which was also adopted Thursday night in a partisan, 21-16 vote — Republicans would be able to advance a package that includes tax cuts that increase the deficit by $4.5 trillion while cutting at least $1.5 trillion from mandatory programs over the coming decade.

The amendment, offered by Rep. Lloyd Smucker (R-Pa.), added language essentially capping the cost of the tax cuts at $4 trillion, with a dollar-for-dollar increase in that ceiling if Republicans cut more spending, up to a total of $2 trillion in cuts.

The effects of that addition will come into focus once Republicans begin to write the party-line package itself and could either diminish the scope of tax cuts GOP lawmakers are able to enact or deepen cuts to federal programs, including safety net benefits like Medicaid health coverage for low-income households.

House Republicans hope to put the budget resolution on the chamber floor for a full vote the last week of February.