Index: wp-admin/install.php
===================================================================
--- wp-admin/install.php	(revision 23983)
+++ wp-admin/install.php	(working copy)
@@ -85,7 +85,7 @@
 		$blog_public = isset( $_POST['blog_public'] );
 
 	$weblog_title = isset( $_POST['weblog_title'] ) ? trim( wp_unslash( $_POST['weblog_title'] ) ) : '';
-	$user_name = isset($_POST['user_name']) ? trim( wp_unslash( $_POST['user_name'] ) ) : 'admin';
+	$user_name = isset($_POST['user_name']) ? trim( wp_unslash( $_POST['user_name'] ) ) : '';
 	$admin_password = isset($_POST['admin_password']) ? trim( wp_unslash( $_POST['admin_password'] ) ) : '';
 	$admin_email  = isset( $_POST['admin_email']  ) ? trim( wp_unslash( $_POST['admin_email'] ) ) : '';