Soccer star Andrés Iniesta, who plays for Japan’s Vissel Kobe, received a warning from the Spanish markets regulator after he promoted trading on cryptocurrency exchange Binance.

Iniesta, who spent much of his career at FC Barcelona and has over 25 million followers on Twitter, wrote that he is “learning how to get started with crypto with @binance #BinanceForAll.”

Spain’s markets regulator, the National Securities Market Commission (CNMV), replied to the tweet, pointing out that “cryptoassets, being unregulated products, carry some significant risks.”

There was no indication whether Iniesta was paid to post the message about Binance, Reuters reported. Former teammates at Barcelona are known to share their enthusiasm for crypto projects.

Iniesta had not responded to a request for a comment through the club’s press office by publication time.

CORRECTION (Nov. 25, 10:38 UTC): Corrects Iniesta’s soccer club, changes photograph.