The US state of Washington has released a letter reminding companies that health benefits must be provided to same-sex married couples.

The Attorney General Bob Ferguson, Insurance Commissioner Mike Kreidler and Human Rights Commission Executive Director Sharon Ortiz all released the letter on Thursday.

Addressed to state employers, insurance companies and benefit plan administrators, it was intended to clarify state laws following the investigation of O’Reilly Automotive Inc by Ferguson’s office.

The Associated Press reports that the company agreed to extend benefits to same-sex couples following the investigation.

Same-sex marriage has been legal in Washington since 2012, and protections against discrimination based on sexual orientation were added in 2006.