Robin Williams entered a rehab facility to help him maintain long-term sobriety in the summer of 2014.
According to TMZ, the actor didn't star using again, but instead decided to seek out a center so he can keep everything in check.
"After working back-to-back projects, Robin is simply taking the opportunity to fine-tune and focus on his continued commitment, of which he remains extremely proud," Williams' rep told the website.
Williams previously battled substance abuse issues and last checked in rehab in 2006.
He died Aug. 11, 2014 at 63. His death was ruled a suicide.