diff --git a/core/modules/dblog/dblog.install b/core/modules/dblog/dblog.install
index ee5bd73..c8d6fa4 100644
--- a/core/modules/dblog/dblog.install
+++ b/core/modules/dblog/dblog.install
@@ -86,6 +86,7 @@ function dblog_schema() {
     'indexes' => array(
       'type' => array('type'),
       'uid' => array('uid'),
+      'severity' => array('severity'),
     ),
   );
 
@@ -126,6 +127,13 @@ function dblog_update_8001() {
 }
 
 /**
+ * Add index to column severity in table watchdog.
+ */
+function dblog_update_8002() {
+  db_add_index('watchdog', 'severity', array('severity'));
+}
+
+/**
  * @} End of "addtogroup updates-7.x-to-8.x".
  * The next series of updates should start at 9000.
  */