diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index f4fe3ce..29fe8be 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -967,8 +967,7 @@ function system_schema() {
       ),
     ),
     'indexes' => array(
-      'fit' => array('fit'),
-      'pattern_outline' => array('pattern_outline'),
+      'fit_pattern_outline' => array('fit', 'pattern_outline'),
       'route_set' => array('route_set'),
     ),
     'primary key' => array('name'),