diff --git a/modules/dblog/dblog.install b/modules/dblog/dblog.install
index 1eedcb0..779516a 100644
--- a/modules/dblog/dblog.install
+++ b/modules/dblog/dblog.install
@@ -85,6 +85,7 @@ function dblog_schema() {
     'indexes' => array(
       'type' => array('type'),
       'uid' => array('uid'),
+      'severity' => array('severity'),
     ),
   );
 
@@ -138,5 +139,12 @@ function dblog_update_7001() {
 }
 
 /**
+ * Add index to column severity in table watchdog.
+ */
+function dblog_update_7002() {
+  db_add_index('watchdog', 'severity', array('severity'));
+}
+
+/**
  * @} End of "addtogroup updates-6.x-to-7.x".
  */