An influential conservative group backed by billionaire brothers Charles and David Koch is questioning a plan to spend $1 trillion on the nation’s infrastructure and warning that one of President Trump’s signature policy initiatives could become a “spending boondoggle.”

In a memo released Friday, Freedom Partners cautions Trump and the Republican-controlled Congress against making the same mistakes that the group says were in the $787 billion federal stimulus bill in 2009. That legislation, passed at former President Barack Obama’s urging, included tax cuts, benefits payments and other spending in addition to infrastructure. It was aimed at boosting the U.S. economy amid the worst recession since the Great Depression.

The stimulus “added nearly a trillion dollars to the national debt and failed to create the so called ‘shovel ready’ infrastructure jobs that were promised,” Nathan Nascimento, the group’s vice president of policy, said in a statement.

“There is a right way and a wrong way to repair and modernize our infrastructure, and it’s time Washington learned from its mistakes,” Nascimento said. “We shouldn’t be asking taxpayers for hundreds of billions of dollars to fund ‘stimulus 2.0’ when there are common sense steps we can take right now to address our infrastructure without spending another dime.”

In his speech Tuesday to Congress, Trump said he wants legislation to support $1 trillion worth of investments in rebuilding roads, bridges, tunnels, airports, and other crumbling infrastructure.