diff --git a/serve.js b/serve.js
index 5ea4d68f..fb8386b4 100755
--- a/serve.js
+++ b/serve.js
@@ -75,6 +75,11 @@ var http = require("http"),
     };
 
 http.createServer(function(request, response) {
+    if (path.normalize(decodeURI(request.url)) !== decodeURI(request.url)) {
+        response.statusCode = 403;
+        response.end();
+        return;
+    }
 
     var uri = url.parse(request.url).pathname,
         filename = path.join(process.cwd(), uri);