Ticket #36831: 36831.patch

wp-includes/plugin.php

@@ -741 +741 @@
  * @return string the filesystem path of the directory that contains the plugin.
  */
 function plugin_dir_path( $file ) {
-        return trailingslashit( dirname( $file ) );
+        return wp_normalize_path( trailingslashit( dirname( $file ) ) );
 }
 
 /**