diff --git a/system/database/DB.php b/system/database/DB.php
index 9b96c7f..1fe44c0 100755
--- a/system/database/DB.php
+++ b/system/database/DB.php
@@ -118,6 +118,13 @@
 	{
 		$query_builder = $query_builder_override;
 	}
+	// Backwards compatibility work-around for keeping the
+	// $active_record config variable working. Should be
+	// removed in v3.1
+	elseif ( ! isset($query_builder) && isset($active_record))
+	{
+		$query_builder = $active_record;
+	}
 
 	require_once(BASEPATH.'database/DB_driver.php');