The brokerage business fiercely fought the new retirement advice rule. But so far for Wall Street, it has been a gift.

The rule requires brokers to act in the best interests of retirement savers, rather than sell products that are merely suitable but could make brokers more money. Financial firms decried the restriction, which began to take effect in June, as limiting consumer choice while raising their compliance costs and potential liability.

But adherence is proving a positive. Firms are pushing customers toward accounts that charge an annual fee on their assets, rather than commissions which can violate the rule, and such fee-based accounts have long been more lucrative for the industry. In earnings calls, executives are citing the Department of Labor rule, known varyingly as the DOL or fiduciary rule, as a boon.

“Primarily because of DOL” and market appreciation, assets are growing in fee-based accounts, said Stifel Financial Corp. Chief Executive Ronald Kruszewski, on a call in July. In an interview, he said such accounts can be twice as costly for clients.

Morningstar Inc. has said $3 trillion in tax-advantaged retirement savings are at stake, but some firms say even more is in play, as policies and marketing filter to nonretirement accounts.