LONDON:

Comic actor Jack Black has vowed to stay sober on movie sets because he is too scared to take drugs or alcohol.

Contactmusic.com reports that Black, who plays a drug addict in the new movie Tropic Thunder, admits he admires his co-star Robert Downey Jr for being able to work under the influence. But he insists his own sobering experience in acting class as a teenager prompted him to kick his bad habits while on the job.

He said, “I had an improvement class in high school and I came stoned one time. I was so paranoid that I never tried to f**k with it again. I marvel at some people’s ability to party and then act. I’m not built that way.”