diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index 6e2fce9718..360a2db83e 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -4353,13 +4353,9 @@ function is_main_network( $network_id = null ) {
  *
  * @since 4.3.0
  *
- * @global wpdb $wpdb WordPress database abstraction object.
- *
  * @return int The ID of the main network.
  */
 function get_main_network_id() {
-	global $wpdb;
-
 	if ( ! is_multisite() ) {
 		return 1;
 	}
@@ -4372,12 +4368,8 @@ function get_main_network_id() {
 		// If the current network has an ID of 1, assume it is the main network.
 		$main_network_id = 1;
 	} else {
-		$main_network_id = wp_cache_get( 'primary_network_id', 'site-options' );
-
-		if ( false === $main_network_id ) {
-			$main_network_id = (int) $wpdb->get_var( "SELECT id FROM {$wpdb->site} ORDER BY id LIMIT 1" );
-			wp_cache_add( 'primary_network_id', $main_network_id, 'site-options' );
-		}
+		$_networks = get_networks( array( 'fields' => 'ids', 'number' => 1 ) );
+		$main_network_id = array_shift( $_networks );
 	}
 
 	/**