Zac Efron will always be all in this together with Matthew Perry.

While accepting his star on the Hollywood Walk of Fame Dec. 11, the High School Musical alum paid tribute to his former 17 Again costar, who was found dead in his Los Angeles home in October at age 54. 

After thanking friends Miles Teller and Jeremy Allen White, "I really also want to mention someone that's not here today," Efron said, "and that's Matthew Perry, who was so kind and generous with me when we worked on 17 Again."

For Efron—who starred as the younger version of Perry's character Mike O'Donnell in the 2009 movie—collaborating with the Friends star and director Burr Steers will always be a career highlight.

"It really did propel me and motivate me in so many ways," the 36-year-old shared. "It really pushed me into the next chapter of my career. And for that, thank you so much Matthew, thinking about you a lot today."