diff --git a/src/wp-includes/class-wp-network.php b/src/wp-includes/class-wp-network.php
index b1d46b7ce0..d33f210dab 100644
--- a/src/wp-includes/class-wp-network.php
+++ b/src/wp-includes/class-wp-network.php
@@ -228,6 +228,7 @@ class WP_Network {
 		 * @param WP_Network $network      The network object for which the main site was detected.
 		 */
 		$main_site_id = (int) apply_filters( 'pre_get_main_site_id', null, $this );
+
 		if ( 0 < $main_site_id ) {
 			return $main_site_id;
 		}
@@ -236,8 +237,10 @@ class WP_Network {
 			return (int) $this->blog_id;
 		}
 
-		if ( ( defined( 'DOMAIN_CURRENT_SITE' ) && defined( 'PATH_CURRENT_SITE' ) && DOMAIN_CURRENT_SITE === $this->domain && PATH_CURRENT_SITE === $this->path )
-			|| ( defined( 'SITE_ID_CURRENT_SITE' ) && SITE_ID_CURRENT_SITE == $this->id ) ) {
+		if ( ( defined( 'DOMAIN_CURRENT_SITE' ) && defined( 'PATH_CURRENT_SITE' )
+			&& DOMAIN_CURRENT_SITE === $this->domain && PATH_CURRENT_SITE === $this->path )
+			|| ( defined( 'SITE_ID_CURRENT_SITE' ) && (int) SITE_ID_CURRENT_SITE === $this->id )
+		) {
 			if ( defined( 'BLOG_ID_CURRENT_SITE' ) ) {
 				$this->blog_id = (string) BLOG_ID_CURRENT_SITE;