diff --git a/src/wp-includes/ms-functions.php b/src/wp-includes/ms-functions.php
index 2f16281754..94418ad350 100644
--- a/src/wp-includes/ms-functions.php
+++ b/src/wp-includes/ms-functions.php
@@ -1422,10 +1422,12 @@ Disable these notifications: %4$s'
 	 * to the network administrator.
 	 *
 	 * @since MU (3.0.0)
+	 * @since 5.4.0 The `$blog_id` parameter was added.
 	 *
-	 * @param string $msg Email body.
+	 * @param string $msg     Email body.
+	 * @param int    $blog_id The new site's ID.
 	 */
-	$msg = apply_filters( 'newblog_notify_siteadmin', $msg );
+	$msg = apply_filters( 'newblog_notify_siteadmin', $msg, $blog_id );
 
 	/* translators: New site notification email subject. %s: New site URL. */
 	wp_mail( $email, sprintf( __( 'New Site Registration: %s' ), $siteurl ), $msg );