we have to start the transaction before we can set the isolation level

lib/transaction.js

@@ -37,11 +37,14 @@ Transaction.prototype.rollback = function() {
 }
 
 Transaction.prototype.prepareEnvironment = function(callback) {
-  var self = this
+  var self             = this
+    , connectorManager = self.sequelize.transactionManager.getConnectorManager(this.id)
 
-  this.setIsolationLevel(function() {
-    self.setAutocommit(function() {
-      self.begin(callback)
+  this.begin(function() {
+    self.setIsolationLevel(function() {
+      self.setAutocommit(function() {
+        connectorManager.afterTransactionSetup(callback)
+      })
     })
   })
 }