diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index b78612454b..ad79494443 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -2252,6 +2252,7 @@ function register_deactivation_hook($file, $function) {
 }
 
 function plugin_basename($file) {
+	$file = preg_replace('|\\\\+|', '\\\\', $file);
 	$file = preg_replace('/^.*wp-content[\\\\\/]plugins[\\\\\/]/', '', $file);
 	return $file;
 }