U.S. home prices rose at a faster pace in July as the housing market continued to show strength in the midst of the coronavirus outbreak.

The S&P CoreLogic Case-Shiller 20-city home price index, released Tuesday, rose 3.9% in July from a year earlier, up from a 3.5% annual gain in June. The July gain was slightly higher than economists had expected.

The 20-city index excluded prices from the Detroit metropolitan area index because of delays related to pandemic at the recording office in Wayne County, which includes Detroit.

Phoenix (up 9.2%), Seattle (7%) and Charlotte, North Carolina (6%), reported the biggest year-over-year gains. Sixteen of the 19 cities saw prices rise at a faster pace than they did in June. The smallest gains came in Chicago (up 0.8%) and New York (1.3%).

Helped by rock-bottom mortgage rates, the U.S. housing market has largely withstood the economic fallout from the COVID-19 outbreak. The Commerce Department reported last week that sales of new homes rose a solid 4.8% in August after surging 13.9% in July.

Home prices are being pushed higher by a shortage of available properties.

“Home prices continued to push pandemic-related uncertainties aside and reach new heights into the summer months, as demand for housing outpaced supply,” said economist Matthew Speakman of the real estate firm Zillow. “An unprecedented lack of for-sale homes combined with persistently low mortgage rates have stoked a competition for housing in recent months that will not relent.″