Judas Priest was high on Sharon Osbourne's list to get for Black Sabbath's Back to the Beginning concert on Saturday in Birmingham, England.
But they couldn't make it because they were playing in Hanover, Germany that day as part of the Scorpions 60th anniversary concert.
To make up for missing the show, Priest have released a cover of "War Pigs" along with a performance video.
The clip includes guitarist Glenn Tipton, who no longer tours with the band because of Parkinson's disease, which also afflicts Ozzy Osbourne.
Priest wrote about the cover, "We are honored to show our love for Ozzy and Black Sabbath with our homage to 'War Pigs.' A song we play at every show around the world that fans sing along to -- reinforcing their love as well for the legendary Prince of Darkness!"
Sabbath recorded "War Pigs" for their second album, 1970's Paranoid.