Ticket #22661: 22661.2.patch

src/wp-includes/load.php

@@ -390 +390 @@
  * @since 3.0.0
  */
 function wp_start_object_cache() {
-        global $blog_id;
+        global $blog_id, $_wp_using_ext_object_cache;
 
         $first_init = false;
         if ( ! function_exists( 'wp_cache_init' ) ) {
                 if ( file_exists( WP_CONTENT_DIR . '/object-cache.php' ) ) {
                         require_once ( WP_CONTENT_DIR . '/object-cache.php' );
-                        if ( function_exists( 'wp_cache_init' ) )
+                        if ( function_exists( 'wp_cache_init' ) && ! isset( $_wp_using_ext_object_cache ) ) {
                                 wp_using_ext_object_cache( true );
+                        }
                 }
 
                 $first_init = true;