diff --git a/package.json b/package.json
index e40f350..afc8147 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "janus-videoroom-client",
-  "version": "2.0.2",
+  "version": "2.0.3",
   "main": "src/janus.js",
   "scripts": {
     "test": "mocha -R spec --full-trace test/*-spec.js"
@@ -27,4 +27,5 @@
   "devDependencies": {
     "mocha": "3.0.1"
   }
+
 }
diff --git a/src/transaction.js b/src/transaction.js
index 1dac34a..2b214e0 100644
--- a/src/transaction.js
+++ b/src/transaction.js
@@ -30,9 +30,9 @@ class InvalidTransactionState extends Error {
     constructor(transaction) {
         super();
         this.name = this.constructor.name;
-        this.message = 'Invalid transaction state ' + this.transaction.getState();
-        this.transaction = transaction;
+        this.message = 'Invalid transaction state ' + transaction.getState();
         this.state = transaction.getState();
+        this.transaction = transaction;
     }
 }
 
diff --git a/test/transaction-spec.js b/test/transaction-spec.js
index 4c21550..23846ea 100644
--- a/test/transaction-spec.js
+++ b/test/transaction-spec.js
@@ -2,6 +2,7 @@
 
 var Transaction = require('../src/transaction').Transaction;
 var TransactionTimeoutError = require('../src/transaction').TransactionTimeoutError;
+var InvalidTransactionState = require('../src/transaction').InvalidTransactionState;
 var ClientResponse = require('../src/client/response').ClientResponse;
 var assert = require('chai').assert;
 var validator = require('validator');
@@ -141,4 +142,30 @@ describe('Transaction', function(){
             done();
         }).start();
     });
+
+    it('should throw an error, due to multiple calls of start', function(done){
+        var transaction = new Transaction({
+            request: request,
+            client: clientMock
+        });
+        transaction.onSent(()=>{
+        }).start();
+        transaction.onError((err)=>{
+            assert.instanceOf(err, InvalidTransactionState);
+            done();
+        }).onSent(()=>{
+        }).start();
+    });
+
+    it('should throw an error, due to invalid call of response', function(done){
+        var transaction = new Transaction({
+            request: request,
+            client: clientMock
+        });
+        transaction.onError((err)=>{
+            assert.instanceOf(err, InvalidTransactionState);
+            done();
+        });
+        transaction.response(new ClientResponse(request, request));
+    });
 });