The faculty union at Long Island University Wednesday night announced an agreement to end a 12-day lockout of professors at the university's Brooklyn campus.

A statement from the Long Island Faculty Federation, which is affiliated with the American Federation of Teachers, said the lockout is over and a mediator will be used to resolve disputes over a new contract. While that process plays out, the expired contract will be in effect, until the end of May, if necessary. The agreement is similar to one proposed earlier by the union and rejected by the administration. The difference is that the contract extension is for a longer period of time and covers the academic year that just started.

Union leaders said they were happy with the deal -- and confident a new contract could be reached.

The university issued a statement from Gale Haynes, vice president, chief operating officer and university counsel, that said the longer time period of the contract extension enabled the administration to support the deal. "The union’s commitment not to strike during this academic year provides us enough runway to reach a reasonable and fair agreement, while providing our students the ability to continue their studies uninterrupted. That has always been our intention. Mediation is a positive step to that end," Haynes said.

The lockout ended after a day on which students held a mass walkout to protest the lockout of 400 regular faculty members. Students have used social media to share dissatisfaction with last-minute instructor replacements and class cancellations since the lockout began earlier this month over stalled contract negotiations between the university and its faculty union. They shared similar complaints during the walkout. Video footage of the protest shows students exiting the campus via a gate to join their picketing professors on the other side. Long Island University students were joined by student supporters from nearby City University of New York campuses.

The central dispute in the contract negotiations is over how quickly to close a pay gap for faculty members at the two main LIU campuses. The union says the gap is unfair to those who teach in Brooklyn, and the administration says that it can't afford to close the gap at the speed the union is proposing.

But the dispute has attracted attention because of the tactic used by the administration more than the disagreement itself. Plenty of negotiations between faculty unions and administrators are tense, and some (including several in the past at LIU) have led to strikes. But it is unprecedented in the history of academic labor unions in the United States for an administration to effectively dismiss all faculty members and replace them with temporary workers (and have administrators teach).

On social media, union members voiced joy Wednesday night.

I am seriously crying, loudly! Is it true? WE ARE GOING BACK TO CLASS??? #liulockout — Magz (@Prof_Magz) September 15, 2016

Jessica Rosenberg, president of the faculty union, issued this statement: “The whole LIU Brooklyn community, and the larger labor community of New York City, the state and the nation, came together to tell the administration to end this lockout. After 12 days of intransigence, the LIU administration discovered that denying students the education they deserve is never a successful strategy. The LIU faculty is relieved this is over and is looking forward to immediately returning to the classroom to get started with the semester. We look forward to a productive outcome as bargaining progresses in the coming weeks.”

Faculty advocates far beyond LIU said the lockout represented an attack on a system of higher education in which the role of professors is respected. Writing on the "Academe" blog, Gail Stygall, a professor of English at the University of Washington, said, "If the administration of this university is able to overturn the fundamental structure of faculty shared governance, then we are all in danger of seeing the destruction of the colleges and universities into customers and faculty-free curriculum."

John Warner, a blogger for Inside Higher Ed, linked the replacement of LIU's faculty members with temporary instructors with the way much of higher education uses adjuncts.

"LIU Brooklyn is the ultimate expression of a much broader trend that has established the labor of teaching as essentially fungible. As long as someone is available to stand in front of the room in the role of 'professor,' LIU Brooklyn administration seems to believe that education is happening," Warner wrote. "The same trend is evident in the adjunctification of faculty, where little concern is given to whether or not an instructor will be part of the institution for longer than a semester, or in some cases have the bare minimum of support necessary to teach their courses."

Classes at LIU Brooklyn will resume Thursday.