diff --git a/lib/session.js b/lib/session.js
index ade1b91..88b08f6 100644
--- a/lib/session.js
+++ b/lib/session.js
@@ -17,7 +17,7 @@ var log    = require('winston'),
 function smsResp(status, callback) {
 	var sms   = this,
 	    tasks = [],
-	    localSmsId,
+	    params,
 	    err,
 	    i;
 
@@ -54,17 +54,21 @@ function smsResp(status, callback) {
 	// Build async tasks to run the responses in parallel
 	i = 0;
 	while (sms.pduObjs[i] !== undefined) {
-		if (sms.pduObjs[i].pduObj.params.esm_class === 0x40) {
-			localSmsId = sms.smsId + '-' + (i + 1);
+		if (sms.smsId) {
+			if (sms.pduObjs[i].pduObj.params.esm_class === 0x40) {
+				params = {'message_id': sms.smsId + '-' + (i + 1)};
+			} else {
+				params = {'message_id': sms.smsId};
+			}
 		} else {
-			localSmsId = sms.smsId;
+			params = {};
 		}
 
 		tasks[i] = sms.session.sendReturn.bind(
 			sms.session,
 			sms.pduObjs[i].pduObj,
 			status,
-			{'message_id': localSmsId},
+			params,
 			false
 		);
 
diff --git a/package.json b/package.json
index 995d889..dbb544a 100644
--- a/package.json
+++ b/package.json
@@ -29,7 +29,7 @@
 		"url": "https://github.com/larvit/larvitsmpp",
 		"type": "git"
 	},
-	"version": "0.1.2",
+	"version": "0.1.3",
 	"readmeFilename": "README.md",
 	"readme": "larvitsmpp",
 	"bugs": {