MESSAGE_TYPE.CONNACK endless loop

Once connection established, paho client executes onSuccess callback endlessly, that is the following part of code is executed over and over again (paho-mqtt.js:1269):

case MESSAGE_TYPE.CONNACK:
this._connectTimeout.cancel();
if (this._reconnectTimeout)

However, server sends CONNACK only once:
1545401288: New client connected from as CLIENT-3331ad84-92c0-514f-a26e-c3c8fd186b76 (c1, k60, u'').
1545401288: Sending CONNACK to CLIENT-3331ad84-92c0-514f-a26e-c3c8fd186b76 (0, 0)

Browser: Chrome

Server: Eclipse Mosquitto 1.5.5

OS: Raspberry Jessie

Client js code:

`
function guid() {
function s4() {
return Math.floor((1 + Math.random()) * 0x10000)
.toString(16)
.substring(1);
}
return s4() + s4() + "-" + s4() + "-" + s4() + "-" +
s4() + "-" + s4() + s4() + s4();
}

host = <removed>;
port = <removed>
username = <removed>;
password = <removed>;
var client = new Paho.Client(host, port, "CLIENT-" + guid());

// set callback handlers
client.onConnectionLost = onConnectionLost;
client.onMessageArrived = onMessageArrived;

// connect the client
client.connect({
onSuccess:onConnect,
userName:username,
password:password,
useSSL:true
});

// called when the client connects
function onConnect() {
// Once a connection has been made, make a subscription and send a message.
console.log("onConnect");
}

// called when the client loses its connection
function onConnectionLost(responseObject) {
if (responseObject.errorCode !== 0) {
console.log("onConnectionLost:"+responseObject.errorMessage);
}
}

// called when a message arrives
function onMessageArrived(message) {
console.log("onMessageArrived:"+message.payloadString);
}
`

Regards,
Victor