diff --git a/lib/server/beautify.js b/lib/server/beautify.js
index 47ad7482..c99ab5e4 100644
--- a/lib/server/beautify.js
+++ b/lib/server/beautify.js
@@ -19,7 +19,7 @@
         if (!beautify)
             callback(Error('Beautify not installed'));
         else if (!is)
-            callback(Error('File should be: ' + EXT));
+            callback(Error('Supported file types: ' + EXT.join(', ')));
         else
             fs.readFile(name, 'utf8', function(error, data) {
                 var result;