diff --git a/mediation-old/src/main/java/com/wso2telco/dep/mediator/impl/ussd/NorthBoundUSSDSubscriptionHandler.java b/mediation-old/src/main/java/com/wso2telco/dep/mediator/impl/ussd/NorthBoundUSSDSubscriptionHandler.java
index 242f055..09806f8 100644
--- a/mediation-old/src/main/java/com/wso2telco/dep/mediator/impl/ussd/NorthBoundUSSDSubscriptionHandler.java
+++ b/mediation-old/src/main/java/com/wso2telco/dep/mediator/impl/ussd/NorthBoundUSSDSubscriptionHandler.java
@@ -124,7 +124,8 @@ public boolean handle(MessageContext context) throws Exception {
         // request creation
         subscriptionGatewayRequestDTO.setClientCorrelator(jsonBody.getJSONObject("subscription").getString("clientCorrelator"));
 
-        if (jsonBody.getJSONObject("subscription").getJSONObject("callbackReference").has("callbackData")) {
+        if (jsonBody.getJSONObject("subscription").getJSONObject("callbackReference").has("callbackData") 
+        		&& !jsonBody.getJSONObject("subscription").getJSONObject("callbackReference").isNull("callbackData")) {
             callbackReference.setCallbackData(jsonBody.getJSONObject("subscription").getJSONObject("callbackReference").getString("callbackData"));
         }