The rocker was thought to be clean for 20 years

Aerosmith‘s Steven Tyler has checked into rehab in California at the age of 60.

The singer was thought to have been clean for over 20 years after struggling with drug problems in the 1970s and ’80s, but is now suffering from an unspecified substance abuse problem.

Tyler, once known along with guitarist Joe Perry as ‘The Toxic Twins‘, has checked into Las Encinas Hospital in Pasadena, according to US Magazine.

The clinic is used as the location for American reality TV show ‘Celebrity Rehab’.

Tyler was diagnosed with Hepatitis C, contracted from drug paraphernalia, in 2003, but is now free of the disease, which has also affected former drug users such as Marianne Faithfull and David Crosby, following intensive chemotherapy.