The Centers for Disease Control and Prevention has extended its “no-sail order” for cruise ships through the end of September, preventing vessels from sailing in U.S. waters out of concern over the COVID-19 pandemic.

The extension is the second for an order that dates back to March 14 and was issued after a series of coronavirus outbreaks on cruise ships. The latest extension was set to expire on July 24.

The move probably won’t dramatically change the timeline for the biggest cruise lines in returning to the seas. Last month, industry group Cruise Lines International Association said it would suspend voyages from U.S. ports until Sept. 15. Carnival Corp., Royal Caribbean Cruises Ltd. and Norwegian Cruise Line Holdings Ltd. are all association members.