Fort Greely, Alaska is home to one of America’s two domestic missile defense bases. Now it’s getting armored against high-altitude electromagnetic energy attacks—like the kind emitted from nuclear blasts.

It’s a far-fetched scenario, but the Pentagon is spending millions on a bunker designed to protect against exactly that. According to contract documents from the Army Corps of Engineers, the military plans to spend $44 million on an “HEMP-protected” bunker housing the base’s missile launch control systems.

By HEMP, the contract is referring to high-altitude electromagnetic pulses. The base at Fort Greely houses anti-ballistic missile interceptors stored in silos, and can also control and direct interceptors fired from a similar site at Vandenberg Air Force base in California.

It’s worth noting the money is pocket change compared to the $41 billion the Pentagon is spending on its ground-based mid-course defense program through 2017. The plan calls for installing dozens of missile interceptors in Alaska and California.

These interceptors carry kinetic kill vehicles designed to impact and destroy ballistic missiles during their mid-course phase. Mid-course defense refers to the flight pattern of ballistic missiles as they travel through space—and before they reenter the atmosphere traveling at extremely high speeds.

But a missile defense site wouldn’t count for much if it could be knocked out by EMP—essentially waves of highly-charged energy that can override electronic circuits.

Missile defense boosters in Congress have for years warned about the threat of a rogue state exploding a nuke high above North America, unleashing waves of energy that fry critical infrastructure, electronics and collectively throwing us back into the 19th century.

The science behind the doomiest EMP scenarios isn’t well supported. A 2010 study in The Space Review by nuclear physicist Yousaf Butt sketched out a worst-case scenario of an EMP attack. Turns out, it would likely disrupt communications—in the most dire case—in only a single state-sized area.

That would be costly, but there’s also a conceptual problem with the idea. If you’re a mad dictator with a single nuke and need to cause the greatest amount of destruction you can with it, you may as well just nuke a city.

You’re bringing on massive retaliation in either case.