U.S. Senator Bernie Sanders’ presidential campaign will limit the hours staffers will work to 42 or 43 hours a week to ensure employees are paid $15 an hour, according to the Des Moines Register.

The senator defended his campaign Friday in an interview with the Iowa paper amid leaked information published in the Washington Post illustrating an internal labor dispute among staffers that had been playing out for months.

Unionized campaign employees demanded a $15 per hour wage, citing the senator’s own words in D.C. and on the campaign trail. Their boss has been one of the nation’s leading voices pushing to raise the federal minimum wage to $15 an hour for years.

In defending his campaign operations while in Iowa, Sanders touted the fact that his was the first campaign to unionize its employees.

“I’m very proud to be the first presidential candidate to recognize a union and negotiate a union contract,” Sanders told the Register. “And that contract was ratified by the employees of the campaign, and it not only provides pay of at least $15 an hour, it also provides, I think , the best health care benefits that any employer can provide for our field organizers.

The campaign’s decision to limit the hours worked of its staff adds further legitimacy to arguments made by those who have opposed such a mandatory spike in wages arguing that employers would be forced to cut down employee hours. Opponents of raising the minimum wage also argue it would require employers to lay off staff, though the Sanders campaign has not indicated whether it would lay off employees or freeze hiring.

Sanders voiced his frustration that the details of his campaign’s labor dispute was leaked to the press.

“It does bother me that people are going outside of the process and going to the media,” Sanders told the Des Moines Register. “That is really not acceptable. It is really not what labor negotiations are about, and it’s improper.”

According to the Washington Post, field organizers for the Sanders campaign are only paid an annual salary of $36,000 a year, and are not paid by hours worked. Regional field directors for the campaign are paid $48,000 and statewide department directors are paid $90,000 a year.

Staffers however, noted in a letter meant for the campaign manager, Faiz Shakir, that field staffers often worked at least 60 hours per week, exceeding the hours of a regular work week and bringing down their hourly rate to $13 an hour.

A proposal from staff, as reported by the Post, urged the campaign to bump up the pay for field organizers to $46,800 a year and $62,400 for the regional field directors.