It’s bad enough that the average stock mutual fund lost something like 40 percent of investors’ money last year, and many bond funds lost money too. Now Morningstar’s Russel Kinnel says investors need to watch out for higher fees on their shrinking accounts.

The problem is that many funds use a system of “breakpoints,” reducing their fees as assets grow past a certain level. As assets fall — and the bear market has knocked industrywide assets down to $5.9 trillion from $8 trillion at the beginning of 2008 — fees automatically go up.

Last year, Kinnel says, the average expense ratio dropped by a basis point (a hundredth of a percentage point) to 0.87 percent. This year, he says, the trend is in the other direction:

Domestic equity funds’ weighted average could rise by 2 basis points. International could pop up by 4 basis points. Taxable bonds should be the same, but munis could pop 4 basis points.

That doesn’t sound like a lot — a basis point is a dollar on a $10,000 investment — and Kinnel says the increase is defensible at a firm like Vanguard, which generally keeps costs low. In other cases, though, he says investors should cry foul:

,,, what about places where expenses are above average? In those cases, I’d like to see fund directors and fund companies alike pushing back on higher costs and saying that they’re going to take a hit along with shareholders and hold the line on higher costs in light of the big losses suffered by shareholders. But in most cases that won’t happen.