diff --git a/modules/system/system.install b/modules/system/system.install
index 43c7383..78458ed 100644
--- a/modules/system/system.install
+++ b/modules/system/system.install
@@ -1460,6 +1460,7 @@ function system_schema() {
       'expire' => array('expire'),
     ),
     'primary key' => array('name'),
+    'mysql_engine' => 'MEMORY',
   );
 
   $schema['sequences'] = array(