AT&T has agreed to pay a $5.25 million fine to settle an investigation into a pair of nationwide 911 outages that occurred in early 2017. The Federal Communications Commission said the first outage, on March 8th, lasted about five hours and affected 12,600 callers. The second, on May 1st, lasted 47 minutes and resulted in 2,600 failed 911 calls.

“Such preventable outages are unacceptable,” the FCC wrote in a statement announcing the settlement. “Robust and reliable 911 service is a national priority, as repeatedly expressed by both Congress and the Commission.”

AT&T failed to “quickly, clearly, and fully notify” affected call centers

In addition to the fines, AT&T is also required to make changes to help minimize issues should an outage happen again and to make sure it informs the proper parties about such outages. The FCC says AT&T failed to “quickly, clearly, and fully notify” the affected 911 call centers.

The outages impacted people on AT&T’s network using Voice over LTE, which many modern phones will default to if the service is supported. AT&T had been making network changes on those days, and they apparently went awry, preventing 911 calls from being routed to call centers.

“Providing access to emergency 911 services is critically important, and to that end we cooperated with the FCC in their review,” an AT&T spokesperson said in a statement. “These events resulted from planned network changes that inadvertently interfered with the routing of 911 calls. We’ve taken steps to prevent this from happening again.”

This is a really small fine for AT&T to pay (the company brought in $38 billion in just its last reported quarter, before it added in all of Time Warner), but it’s meant to be a reminder of how critical 911 service is — there’s no time when an outage is acceptable. And while outages are going to happen now and then, there’s a chain of events that are supposed to take place to make sure that they’re mitigated, and AT&T apparently didn’t follow those, leading to today’s fine.

Update June 28th, 7:22PM ET: This story has been updated to include a statement from AT&T.