Index: wp-includes/default-constants.php
===================================================================
--- wp-includes/default-constants.php	(revision 15277)
+++ wp-includes/default-constants.php	(working copy)
@@ -262,7 +262,7 @@
 		define( 'EMPTY_TRASH_DAYS', 30 );
 
 	if ( !defined('WP_POST_REVISIONS') )
-		define('WP_POST_REVISIONS', true);
+		define('WP_POST_REVISIONS', 30);
 }
 
 /**