diff --git a/includes/Installer/DatabaseUpdater.php b/includes/Installer/DatabaseUpdater.php
index 8ed996b9dee..733a3210096 100644
--- a/includes/Installer/DatabaseUpdater.php
+++ b/includes/Installer/DatabaseUpdater.php
@@ -1380,7 +1380,7 @@ public function purgeCache() {
 		// ObjectCache
 		$this->db->newDeleteQueryBuilder()
 			->deleteFrom( 'objectcache' )
-			->where( ISQLPlatform::ALL_ROWS )
+			->where( "keyname NOT LIKE '%:MWSession:%'" )
 			->caller( __METHOD__ )
 			->execute();