diff --git a/lib/layer.js b/lib/layer.js
index 6a4408f..1455a94 100644
--- a/lib/layer.js
+++ b/lib/layer.js
@@ -217,7 +217,7 @@ Layer.prototype.match = function match (path) {
  */
 
 function decodeParam (val) {
-  if (typeof val !== 'string' || val.length === 0) {
+  if (typeof val !== 'string' || val.length === 0 || val.indexOf('%') === -1) {
     return val
   }