diff --git a/src/Util/Proxy.php b/src/Util/Proxy.php
index cb8042f1b1..b46b4cd7d6 100644
--- a/src/Util/Proxy.php
+++ b/src/Util/Proxy.php
@@ -49,19 +49,6 @@ class Proxy
 	const PIXEL_MEDIUM = 640;
 	const PIXEL_LARGE  = 1024;
 
-	/**
-	 * Accepted extensions
-	 *
-	 * @var array
-	 * @todo Make this configurable?
-	 */
-	private static $extensions = [
-		'jpg',
-		'jpeg',
-		'gif',
-		'png',
-	];
-
 	/**
 	 * Private constructor
 	 */