Wednesday marked the 15th anniversary of Joss Whedon’s short-lived but beloved sci-fi series premiering on Fox, and Fillion, who starred as the spaceship Serenity’s owner and captain, Malcolm “Mal” Reynolds, celebrated the milestone with a message about how much Firefly means to him.

Alongside a picture of himself on set with Whedon, Fillion wrote, “Has it really been 15 years since a little sci fi show that couldn’t, did? I would be hard pressed to list all the ways in which Firefly has changed, blessed, pushed, lifted, and humbled me. I made my closest friends there, and even lost one along the way. I’ve often said that Firefly is close to my heart, but I think more accurately, my heart still lives there. But, there’s no place I’d rather be- you know how it goes. For those of you in the fold, a knowing nod between us. For those that are not- we’ll see you soon enough. #Browncoats.”

Has it really been 15 years since a little sci fi show that couldn’t, did? I would be hard pressed to list all the ways in which Firefly has changed, blessed, pushed, lifted, and humbled me. I made my closest friends there, and even lost one along the way. I’ve often said that Firefly is close to my heart, but I think more accurately, my heart still lives there. But, there’s no place I’d rather be- you know how it goes. For those of you in the fold, a knowing nod between us. For those that are not- we’ll see you soon enough. #Browncoats

A post shared by Nathan Fillion (@natefillion) on Sep 20, 2017 at 3:32pm PDT

Debuting in 2002, Firefly was canceled after 11 of the 14 produced episodes aired. Strong fan support helped continue the story on the big screen with the 2005 release of Serenity.