George Takei is remembering his longtime friend and Star Trek co-star Walter Koenig following the actor’s death at 90 .

Koenig, best known for playing Ensign Pavel Chekov in the original Star Trek series and several of the franchise’s movies, died Sunday at his home in North Hollywood. His representative confirmed the news, saying Koenig died of natural causes with his daughter and niece by his side.

Takei, who played Hikaru Sulu alongside Koenig’s Chekov, shared a touching tribute to his friend on social media Monday.

“My heart is heavy,” Takei began.

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George Takei and Walter Koenig Were Friends for Nearly Six Decades

Takei recalled meeting Koenig when they were both part of the original Star Trek cast in the 1960s.

“Walter and I met on the bridge of the Enterprise in the 1960s, and we stayed friends for nearly six decades,” Takei wrote.

Their friendship continued long after the original series ended.…