diff --git a/includes/class-mention.php b/includes/class-mention.php
index 8f782b5..d55e5f2 100644
--- a/includes/class-mention.php
+++ b/includes/class-mention.php
@@ -15,6 +15,7 @@ class Mention {
 	 */
 	public static function init() {
 		\add_filter( 'the_content', array( self::class, 'the_content' ), 99, 2 );
+		\add_filter( 'activitypub_extract_mentions', array( self::class, 'extract_mentions' ), 99, 2 );
 	}
 
 	/**
@@ -146,4 +147,23 @@ class Mention {
 
 		return new WP_Error( 'activitypub_no_inbox', \__( 'No "Inbox" found', 'activitypub' ), $metadata );
 	}
+
+	/**
+	 * Extract the mentions from the post_content.
+	 *
+	 * @param array  $mentions The already found mentions.
+	 * @param string $post_content The post content.
+	 *
+	 * @return mixed The discovered mentions.
+	 */
+	public static function extract_mentions( $mentions, $post_content ) {
+		\preg_match_all( '/@' . ACTIVITYPUB_USERNAME_REGEXP . '/i', $post_content, $matches );
+		foreach ( $matches[0] as $match ) {
+			$link = Webfinger::resolve( $match );
+			if ( ! is_wp_error( $link ) ) {
+				$mentions[ $match ] = $link;
+			}
+		}
+		return $mentions;
+	}
 }