Lea Michele and Cory Monteith attend the 2012 Do Something Awards at Barker Hangar on August 19, 2012 in Santa Monica, California.

Cory Monteith's Glee costars offered birthday wishes online to the late actor and singer Monday, who would have turned 33 were he still alive.

Famous for his role of Finn Hudson, Monteith died in 2013 at the age of 31.

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"I know you're serenading everyone right now.. We love you Cory! Happy Birthday," said Lea Michele, who similarly last year posted a tribute to Twitter.

"Not one day goes by..." said Kevin McHale.

Mark Salling dedicated his Man Crush Monday Instagram post to Monteith, saying, "Miss you more than ever brother."

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And Amber Riley said, "I miss you! Gone but never ever forgotten."

See their posts below

I know you're serenading everyone right now.. We love you Cory! Happy Birthday..?? pic.twitter.com/pbjMFOr06N — Lea Michele (@msleamichele) May 11, 2015

Not one day goes by...?? happy birthday A photo posted by Kevin McHale (@kevinmchale) on May 11, 2015 at 11:28am PDT

I miss you! Gone but never ever forgotten. Happy Birthday brother A photo posted by Amber Riley (@msamberpriley) on May 11, 2015 at 1:19pm PDT