diff --git a/README.md b/README.md
index 0f108cb..316dca8 100644
--- a/README.md
+++ b/README.md
@@ -46,4 +46,5 @@ more details.. https://github.com/ran-jit/tomcat-cluster-redis-session-manager/w
 	* **</session-config>**
 
 ### Note:
+  * All your session attribute values must implement java.io.Serializable.
   * This supports, both redis stand-alone and multiple node cluster based on the redis-data-cache.properties configuration.