A rule requiring investment advisors to act in the best interest of clients saving for retirement was released today despite a six-year campaign to weaken or kill it. Secretary of Labor Thomas Perez and his staff deserve enormous credit for persevering.

The financial services industry made the usual claim that the rule would hurt the people it was supposed to help—essentially, that investors are better off with bad advice than no advice. It also told Congress the rule would be unduly burdensome, while assuring investors there was nothing to worry about, as Senator Elizabeth Warren and Representative Elijah Cummings pointed out.

Let’s hope the financial industry was lying to investors, not Congress, because the rule should have an impact on its bottom line. The only problem is that it doesn’t go far enough. A financial advisor can now be sued for recommending a higher-cost mutual fund over a similar but lower-cost fund without disclosing that he or she is working on commission—a practice that was perfectly legal until today. But the rule doesn’t require that he or she provide information about low-cost index funds and similar investments, even though the original draft rule pointed out that the prevailing view in the academic literature was that such a passive investment strategy was optimal.

It’s unlikely that investors could successfully sue advisors simply for steering them to higher-cost asset classes, as long as the investments are generally considered suitable for people saving for retirement (mutual funds or annuities, for example, and not shares in racehorses). But the mutual fund and insurance industries succeeded in having this spelled out in the final rule and eliminating a safe harbor for broker-dealers offering “high-quality low-fee products… calibrated to track the overall performance of financial markets.” The list of other changes is worth reading and perhaps worrying about, though they may matter little in practice and simply allow the administration to demonstrate its responsiveness while giving lobbyists something to show for their expensive efforts.

The Department of Labor rule applies only to advice relating to tax-favored retirement plans such as 401(k)s and Individual Retirement Accounts. The Securities and Exchange Commission is working on a broader fiduciary rule, but has been slower to move than DOL. Since the SEC’s proposed rule isn’t expected until October—and that’s just a first step—its fate will presumably depend on election results and who is appointed to fill two commission vacancies. In the meantime, the DOL’s groundbreaking rule will protect some of the most vulnerable investors, especially savers who until now have been given highly conflicted advice about rolling over assets from 401(k)s to IRAs. The administration estimates that such conflicts of interest cost retirement savers a whopping $17 billion a year.