Early Wednesday morning, Donald Trump called Jerry Falwell Jr. and woke him up with news the Liberty University president has long been waiting to hear. The new Republican platform, the GOP nominee told Falwell, calls for the repeal of a half-century-old tax law prohibiting churches and tax-exempt institutions from political organizing.

“He was so excited,” Falwell says. “After 30 years of the so-called conservative leaders who have been elected by evangelicals, none of them thought to advocate for the repeal of the Johnson amendment, giving evangelical leaders political free speech. … He thinks it is going to be a revolution in the Christian world.”

The “Johnson Amendment,” as the 1954 law is often called, is a U.S. tax code rule preventing tax-exempt organizations, such as churches and educational institutions, from endorsing political candidates. At the time, then-Senator Lyndon B. Johnson was running for re-election, and he and other members of Congress pushed the amendment to stop support for their political opponents’ campaigns, George Washington University law professor Robert Tuttle has explained. Many have also argued the amendment served to stop black churches from organizing to support the civil rights movement.

“All section 501(c)(3) organizations are absolutely prohibited from directly or indirectly participating in, or intervening in, any political campaign on behalf of (or in opposition to) any candidate for elective public office,” the IRS explains of the rule on its website. “Violating this prohibition may result in denial or revocation of tax-exempt status and the imposition of certain excise taxes.”