President-elect Donald Trump’s pledge to crack down hard on mass migration promises to mean big business for private prisons.

Companies like CoreCivic and Geo Group may be known for profiting from the growing population of incarcerated Americans, but they struck gold after expanding into the operation of detention centers for undocumented migrants on behalf of the U.S. Immigration and Customs Enforcement (ICE). 

Now investors are betting heavily their earnings are set to soar, bidding up shares on Wednesday in the aftermath of Trump’s election. Stock in CoreCivic surged 29% while Geo Group saw an even bigger gain, vaulting 42% in a single session. 

While Trump and his allies have long attacked the Democratic Party for being too soft on crime and too soft on borders, it was Elon Musk—himself an immigrant—who made the issue of illegal migration the core argument why he was spending millions in a risky gamble to return Trump to the White House.

Elon Musk has pushed illegal immigration to the top of Trump agenda

The centibillionaire and owner of X repeatedly claimed Democrats were deliberately opening the floodgates on the southern border, strategically funneling Latino migrants from countries like Venezuela to battleground states where they would be granted asylum and put on a fast track to citizenship. 

In exchange, he warned, the grateful newly naturalized Americans would then vote for the Democrats, eventually turning the whole of the country into a Democratic stronghold like California. (However, exit polls indicate Latino men were the single biggest demographic to swing from Biden in 2020 to Trump in 2024.)

“If Trump doesn’t win, this will be the last real election in America,” Musk told Joe Rogan on Election Day, during which Rogan endorsed Trump. “They will legalize enough illegals to turn the swing states and everywhere will be like California. There will be no escape.”

With Musk likely to wield considerable influence in the next administration, the market now expects companies like CoreCivic and Geo Group to profit.

One million immigrants set to be deported in first wave

Investors betting on a boom in ICE-related profits have good reason. During the Trump administration, the federal government expanded its immigration detention system by over 50%, a move that “overwhelmingly benefitted private prison companies”, according to findings from the American Civil Liberties Union (ACLU). The number of migrants detained reached a peak of 55,000 in 2019.

It didn’t end with Biden’s election either. Even though he immediately issued an executive order ending private prison contracts with the federal government when he took office in January 2021, Biden made one exception—migrant detention facilities.

Following Trump’s election on Tuesday, the new president-elect now has to deliver on a promise to launch the “largest deportation in the history of our country.” Vice President-elect JD Vance suggested his boss should start with 1 million undocumented migrants “and then we can go from there”. 

There’s just one catch that could potentially throw a wrench in the cogs for CoreCivic and Geo Group. Cities and states need to cooperate with ICE, which is not necessarily a given. Some speculate Trump will use the threat of withholding federal funding as a means to force compliance.   

Fortune reached out to CoreCivic and Geo Group for comment, but could not reach a spokesperson by press time. 

This story was originally featured on Fortune.com