For fund managers, sometimes asset flows are too much of a good thing.

Valley Forge, Pa.-based Vanguard is closing its $30 billion Dividend Growth Fund (VDIGX) to new investors after the fund received a surge of inflows in recent years.

“Vanguard is proactively taking steps to slow strong cash flows to help ensure that the advisor’s ability to produce competitive long-term results for investors is not compromised,” said Vanguard CEO Bill McNabb in a statement on Thursday. “We have long been committed to protecting the interests of our funds’ shareholders, and demonstrate this conviction by closing or restricting funds to stem further growth.”

Effective immediately, the fund will no longer accept new accounts. Existing shareholders may continue to invest without limitation. Participants in defined contribution plans with VDIGX as an option and those who invest through technology-driven model portfolios will also be able to continue investing in the fund, according to a company spokesperson.

VDIGX, which is advised by Wellington Management Company, has received $3 billion in net cash inflows over the past six months alone, and has nearly doubled in total assets over the past three years, according to Vanguard. 

Over the past year, VDIGX has outperformed its benchmark, the NASDAQ U.S. Dividend Achievers Select Index, by 65 basis points. The Vanguard mutual fund has also outpaced its benchmark over the past 3-, 5- and 10-year time periods.

Vanguard has acted pre-emptively to restrict cash inflows in other strategies, with several funds currently closed or restricted. The Vanguard Capital Opportunity fund, the Vanguard PRIMECAP fund and the Vanguard PRIMECAP Core Fund are closed to new investor accounts except for specified retail accounts, and the Vanguard Convertible Securities Fund and the Vanguard Wellington Fund are closed to new institutional accounts.

Other Vanguard dividend strategies, like the Vanguard Dividend Appreciation ETF (VIG) and the Vanguard Equity Income Fund (VEIPX), remain open to new investors, says the company spokesperson.