diff --git a/includes/ForkController.php b/includes/ForkController.php
index e5b44c2b501..1cd49e76b54 100644
--- a/includes/ForkController.php
+++ b/includes/ForkController.php
@@ -115,10 +115,10 @@ class ForkController {
 	}
 
 	protected function prepareEnvironment() {
-		global $wgCaches, $wgMemc;
+		global $wgMemc;
 		// Don't share DB or memcached connections
 		wfGetLBFactory()->destroyInstance();
-		$wgCaches = array();
+		ObjectCache::clear();
 		unset( $wgMemc );
 	}
 
diff --git a/includes/objectcache/ObjectCache.php b/includes/objectcache/ObjectCache.php
index 5155c0da9a9..118aadfe27a 100644
--- a/includes/objectcache/ObjectCache.php
+++ b/includes/objectcache/ObjectCache.php
@@ -21,6 +21,13 @@ class ObjectCache {
 		return $object;
 	}
 
+	/**
+	 * Clear all the cached instances.
+	 */
+	static function clear() {
+		self::$instances = array();
+	}
+
 	/**
 	 * Create a new cache object of the specified type.
 	 */