Vanguard on Wednesday said it is planning a 1-for-2 reverse share split of its exchange traded fund indexed to the S&P 500 as the so-called ETF fee war takes a new turn.

“Vanguard expects the split to lower the overall transaction costs to buy and sell VOO shares,” the firm said in a press release. Shares of Vanguard S&P 500 ETF (ticker: VOO) will be offered on a split-adjusted basis on Oct. 24.

“We haven’t heard the last of the ETF fee wars,” said Daniel Wiener, editor of The Independent Adviser for Vanguard Investors.

“[T]he new frontier in low costs is the bid-ask spread and this morning’s announcement that Vanguard is going to do a reverse-split on its S&P 500 ETF shares means it’s swiftly going to halve the bid-ask disparity on the security—all things being equal,” Wiener said in a note Wednesday.

He said Vanguard’s decision to reverse-split VOO is a smart move.

“Will it really matter to the individual investor buying or selling a few hundred or even a few thousand shares of VOO? Probably not. But for the traders looking for every edge and every sliver of savings, it matters,” Wiener added. “Spreads are the new operating expenses in the fee wars …  today’s announcement of a reverse-split signals a new front in the contest for ETF market domination.”

VOO holds assets of about $11 billion and charges an expense ratio of 0.05%.