diff --git a/lib/cookie-sessions.js b/lib/cookie-sessions.js
index f02a583..1ba8947 100644
--- a/lib/cookie-sessions.js
+++ b/lib/cookie-sessions.js
@@ -97,10 +97,10 @@ function extend(obj) {
 
 exports.deserialize = function(secret, timeout, str){
     // Parses a secure cookie string, returning the object stored within it.
-    // Throws an exception if the secure cookie string does not validate.
+    // Ignores cookie if the secure cookie string does not validate.
 
     if(!exports.valid(secret, timeout, str)){
-        throw new Error('invalid cookie');
+        return undefined;
     }
     var data = exports.decrypt(secret, exports.split(str).data_blob);
     return JSON.parse(data);