diff --git a/wp-admin/includes/file.php b/wp-admin/includes/file.php
index 55125f6c73..6c12b3f37a 100644
--- a/wp-admin/includes/file.php
+++ b/wp-admin/includes/file.php
@@ -146,7 +146,7 @@ function wp_tempnam( $filename = '', $dir = '' ) {
 		$dir = get_temp_dir();
 	}
 
-	if ( empty( $filename ) || '.' == $filename ) {
+	if ( empty( $filename ) || '.' == $filename || '/' == $filename ) {
 		$filename = time();
 	}