Drugmaker stocks rose handsomely the day President Trump outlined his new plan for bringing down drug prices–which means Wall Street doesn’t think his plan will work.

Earlier this year, Trump declared that drugmakers are “getting away with murder” through the high prices they charge, and he said the government would bid more aggressively when buying drugs. But his formal plan to lower drug prices, unveiled on May 11 after several delays, does not call for the one move many experts believe would be most effective: A new law that would allow Medicare to negotiate with pharmaceutical providers. Medicare is the largest single purchaser of drugs in the country, yet federal law prohibits the giant program from negotiating on drug prices. Instead, it relies on private-sector partners to get the best prices.

That apparently won’t change under Trump, which is a big victory for an industry that spends $280 million a year lobbying in Washington, more than any other sector. Instead of freeing Medicare to flex its market muscle, Trump is calling for a variety of other reforms and new rules intended to improve competition and force drugmakers to lower prices to get customers. But the uptick in share prices of companies such as Merck (MRK), Pfizer (PFE), Bristol-Myers Squibb (BMY) and Eli Lilly (LLY) suggests investors believe Trump’s plan won’t impact prices enough to threaten revenues or profits.

Trump’s plan identifies several problems with pharmaceuticals in the US health system: List prices and out-of-pocket expenditures by consumers are too high, government programs such as Medicare and Medicaid overpay, and foreign governments pay less than their fair share for drugs developed by American companies. Many experts agree with that diagnosis, although some argue that foreign governments are simply more effective negotiators able to leverage their heft as large drug purchasers to push costs down.

Trump’s solutions include more than a dozen measures meant to provide more information to consumers, so they can comparison shop more effectively, and to make more choices available, which in theory ought to push prices down. Trump wants to explicitly allow pharmacists to help patients get the cheapest medications, which they’re not allowed to do now in some instances. He wants to tighten rules on drugmaker incentive payments so that consumers, not middlemen, get the bounty. Trump even suggested drugmakers should be required to run prices in their ads, so consumers know how much it costs to emulate that happy-looking couple on the beach.