diff --git a/backbone.js b/backbone.js
index 2341c175..b9201a88 100644
--- a/backbone.js
+++ b/backbone.js
@@ -307,7 +307,7 @@
     url : function() {
       var base = getUrl(this.collection) || this.urlRoot || urlError();
       if (this.isNew()) return base;
-      return base + (base.charAt(base.length - 1) == '/' ? '' : '/') + this.id;
+      return base + (base.charAt(base.length - 1) == '/' ? '' : '/') + encodeURIComponent(this.id);
     },
 
     // **parse** converts a response into the hash of attributes to be `set` on