Joaquin Phoenix apologised to inmates at Folsom State Prison in California on Tuesday for messing up a concert and not bringing his Walk The Line co-star Reese Witherspoon with him.
The actor toured the prison and screened his Johnny Cash biopic before playing a handful of the Cash songs he performed as the country hero in the film.
The humble Gladiator star, dressed in Cash's famous all black ensemble, told the 50-plus inmates who caught his tribute show that he hadn't picked up a guitar since the biopic wrapped last year and felt a "little rusty".
But inmates didn't seem to mind as he recalled a famous Cash concert at the California prison, performing the late country icon's standard Folsom Prison Blues.
He made them laugh when he revealed his co-star Witherspoon had hoped to join him on his prison visit, adding: "I know you guys would probably rather see Reese."
But inmate Eric Breland insists Phoenix's performance was extremely moving and the biopic screening was stirring.
He says: "I was in tears. It really surprised me."