diff --git a/wp-admin/includes/file.php b/wp-admin/includes/file.php
index 5cd7a454d6..3754fddfa1 100644
--- a/wp-admin/includes/file.php
+++ b/wp-admin/includes/file.php
@@ -171,6 +171,7 @@ function wp_tempnam($filename = '', $dir = ''){
 	if ( empty($filename) )
 		$filename = time();
 
+	$filename = preg_replace('|\..*$|', '.tmp', $filename);
 	$filename = $dir . wp_unique_filename($dir, $filename);
 	touch($filename);
 	return $filename;