Hayden Panettiere’s ex-fiancé and father of their daughter, Wladimir Klitschko, has paid a touching tribute to the actor on what would’ve been her 37th birthday.

The retired boxing legend posted a photo in remembrance of the late actor on Instagram Aug. 21, five days after the “Heroes” and “Nashville” star was pronounced dead in South Carolina.

“Today is Hayden’s birthday. Instead of celebrating the way we had planned, today we celebrate her life, her spirit, and the love she brought into this world,” he wrote. “I want to thank all of Hayden’s fans, friends, and everyone who has reached out for the incredible outpouring of love and support. At a time filled with so much sadness, your kindness has reminded me that there is still so much good in humanity.”

In his post, Klitschko also called on fans to spread love.

“If you’re reading this, I ask just one thing: even if only for a moment, think about LOVE,” he continued. “Reach out to a friend. Forgive someone. Be kind. Love is a superpower. Use it.

He concluded with a sweet message to Panettiere.

“Happy Birthday, Hayden. ❤️ You are loved, you are missed, and you will never be forgotten,” he wrote.

Klitschko is the father of the couple’s 11-year-old daughter, Kaya, and was engaged to Panettiere before they broke things off in 2018.

He previously shared an emotional message on Instagram two days after Panettiere’s death.

“To our daughter Kaya, I will always speak of her mother with respect and make sure she remembers the person she was,” Klitschko wrote.

Panettiere was found in cardiac arrest on Aug. 16 when emergency personnel responded to a 911 call at a residence where she had been temporarily staying in Greenville, South Carolina, according to a statement by the Greenville County Coroner’s Office. She was declared dead at 2:32 p.m. after EMS workers were unable to resuscitate her.

Dispatch audio from the emergency response references a possible overdose, but no cause or manner of death has been given by authorities.

The Drug Enforcement Agency has joined local authorities in the investigation into her death, a source familiar with the probe told NBC News on Aug. 20.