The default rate for global speculative-grade securities is down at its lowest level since 2015, according to a report published Wednesday by Moody's Investors Service.

The global speculative default rate dropped to 2.9% in August from 3.1% in July, the report says, as just two firms defaulted during the month. August marks the first time that the global default rate has fallen under 3% since 2015, the report notes.

Moody's is projecting that the global default rate will continue declining in the months ahead, and will reach 2.3% in August 2018. Back in August 2016, the rate was up at 4.8%, as turmoil in the commodity sectors pushed the default rate to a seven-year high.

"This benign forecast is a function of a relatively low level of high yield spread and stability in commodity prices," says Sharon Ou, vice president and senior credit officer at Moody's, in a statement.

In the United States, the default rate declined to 3.4% in August, down from 3.6% in prior month. The rate in Europe fell to 2.6% from 2.8%.