edit

lib/Store/Core.php

@@ -682,6 +682,7 @@ class Core
 			'audio/webm' => 'webm',
 			'video/webm' => 'webm',
 			'audio/x-m4a' => 'm4a',
+			'image/webp' => 'webp',
 		);
 
 		if (isset($config[$mine])) {