Six Democratic senators and one independent have asked the Department of Health and Human Services to a delay a new rule that would likely force small businesses to pay more for employee health insurance under the Affordable Care Act, aka Obamacare. The senators warn that if the administration goes ahead with the change it would be “particularly harmful and disruptive” to small businesses.

Starting in 2016, the Obamacare change will require businesses that employ between 51-100 people to purchase insurance in what the government defines as the “small group market,” rather than the market for large group plans. The senators warn that the change will inflate health care costs for those businesses.

“[T]hey could experience higher premiums, less flexibility, and new barriers to coverage. We therefore encourage you to delay the effective date in the definition change for two years so the market can more smoothly transition to the new rules,” the senators wrote in the March 12 letter to HHS Secretary Sylvia Burwell.