WASHINGTON (MarketWatch)—There was good news for the U.S. housing market Thursday morning: A gauge of upcoming sales of existing homes rose last month to the highest level in nine years, the National Association of Realtors reported.

But that jump doesn’t guarantee large sales growth in coming months.

Typically, the pending-home-sales index is a good guide to upcoming closings, leading final sales by a month or two. However, there was a notable breakdown in that relationship last month—the pace of existing-home sales dropped 3.3% in April, even though the pending gauge had climbed up throughout the first quarter of the year.

“Maybe it was just a one-month little puzzle,” said Lawrence Yun, NAR’s chief economist.

However, Yun added that if the gap between pending sales and actual closings persists, then that could indicate an increase in cancellations. Deals are canceled for all sorts of reasons, such as financial issues and problems found during an inspection.

Some economists are concerned about whether the housing market can overcome a variety of challenges this year: Prices are racing higher, with the number of homes for sale lagging demand in many markets, and weak income growth isn’t helping families afford ownership.

“The current low inventory levels, which are placing upward pressure on home prices, remain a bit of a downside risk,” said Derek Lindsey, an analyst with BNP Paribas.

But there are also reasons for housing-market hope. Young families and other first-time buyers are tiptoeing into the market, a trend that will support the broader economy and other homeowners who want to buy a new place. Meanwhile, mortgage rates are still low, keeping down loan costs, a factor that can nudge fence-sitters to become buyers. Along those lines, a prominent housing economist recently increased his forecast for purchase mortgages this year, saying that he expects “moderate but broad-based improvement.”

Doug Duncan, chief economist at federally controlled mortgage-finance giant Fannie Mae FNMA, +2.51% , said Thursday that the pending gauge is “reasonably predictive,” and that he expects April’s jump “will ultimately result in increased sales.”

Economists at Wells Fargo Securities wrote after Thursday’s data release that April’s sales drop for used homes may have been a blip.

“The pending home sales numbers indicate that the monthly decline will be short-lived,” according to Wells Fargo. “Growth appears to be broad based across regions.”