Money market funds (MMFs) are beginning to increase their fees in anticipation of the US Federal Reserve raising interest rates later this year, according to a report from iMoneyNet.

The research firm reported that the average expense ratio for all MMFs was 0.13% in the second quarter, up from an all-time low of 0.11% recorded in the previous three quarters.

“Elevated charged expense ratios were particularly prominent among prime retail and prime institutional funds,” iMoneyNet reported.

T Rowe Price said in its second quarter report that it had reduced some fee waivers, while Charles Schwab and Federated Investors are considering similar moves, iMoneyNet said.

Fund providers were also “slightly less willing” to grant fee waivers to investors in Q2, the group said.

“Overall, 98.5% percent of taxable and tax-free funds absorbed at least some fees, down slightly from 98.6% in the January-to-March quarter,” iMoneyNet said.

Many providers have been waiving some or all fees on cash funds since the Federal Open Market Committee (FOMC) cut the core US interest rate to 0.25% in December 2008 at the height of the financial crisis.

This policy cost providers $6.3 billion last year, according to an estimate from the Investment Companies Institute. Since 2009, $30.1 billion in revenue has been lost due to fee waivers.

The FOMC is widely expected to raise the base interest rate this year, which would mark the first increase since 2006. Several market commentators have recently pushed back their expectations for the timing of this increase, however, having initially pencilled in September’s FOMC meeting.

Related:Market Reads Fed Hike Delay in FOMC Minutes & Fed Rate Rise ‘Not the Only Show in Town’