Sequelize SERIALIZABLE isolation level error

test.js

var Sequelize = require('sequelize');                                                
var Promise = require('bluebird');                                                   
var sequelize = new Sequelize('postgres://realyze@localhost:5432/trans-test');       
                                                                                     
var Transaction = sequelize.define('transaction', {                                     
  value: {                                                                              
    type: Sequelize.DECIMAL(10, 3),                                                     
    field: 'value'                                                                      
  }                                                                                     
});                                                                                     
                                                                                        
Transaction.sync({force: true}).then(function () {                                      
                                                                                        
  function transTest(val) {                                                             
    return sequelize.transaction({isolationLevel: 'SERIALIZABLE'}, function(t) {        
      return Transaction.sum('value', {transaction: t})                                 
        .then(function (balance) {                                                      
          if (balance < 0) {                                                            
            console.log('not enough money');                                            
            return Promise.reject(new Error())                                                                                                                           
          }                                                                             
          return Transaction.create({value: -val}, {transaction: t});                   
        })                                                                              
    });                                                                                 
  }                                                                                     
                                                                                        
  Transaction.create({value: 100})                                                      
    .then(function() {                                                                  
      return Promise.all([transTest(80), transTest(80), transTest(80)]);                
    })                                                                                  
    .then(function(res) {                                                               
      console.log('done');                                                              
    })                                                                                  
    .catch(function(err) {                                                              
      console.error('TRANSACTION ERROR', err);                                          
    })                                                                                  
})