diff --git a/broker/src/main/java/io/moquette/spi/impl/ProtocolProcessor.java b/broker/src/main/java/io/moquette/spi/impl/ProtocolProcessor.java
index 9b93ac8d..abc78ca1 100644
--- a/broker/src/main/java/io/moquette/spi/impl/ProtocolProcessor.java
+++ b/broker/src/main/java/io/moquette/spi/impl/ProtocolProcessor.java
@@ -719,7 +719,8 @@ public class ProtocolProcessor {
 
         // ack the client
         int messageID = msg.variableHeader().messageId();
-        MqttFixedHeader fixedHeader = new MqttFixedHeader(MqttMessageType.UNSUBACK, false, AT_LEAST_ONCE, false, 0);
+        MqttFixedHeader fixedHeader = new MqttFixedHeader(MqttMessageType.UNSUBACK, false, AT_MOST_ONCE,
+                                                         false, 0);
         MqttUnsubAckMessage ackMessage = new MqttUnsubAckMessage(fixedHeader, from(messageID));
 
         LOG.debug("Sending UNSUBACK message. CId={}, topics={}, messageId={}", clientID, topics, messageID);
diff --git a/tools_scripts/integration/issue410UnsubscribeAckFormat.groovy b/tools_scripts/integration/issue410UnsubscribeAckFormat.groovy
new file mode 100644
index 00000000..b728a9be
--- /dev/null
+++ b/tools_scripts/integration/issue410UnsubscribeAckFormat.groovy
@@ -0,0 +1,81 @@
+@GrabResolver(name='Paho', root='https://repo.eclipse.org/content/repositories/paho-releases/')
+@Grab(group='org.eclipse.paho', module='mqtt-client', version='0.4.0')
+
+import org.eclipse.paho.client.mqttv3.MqttClient
+import org.eclipse.paho.client.mqttv3.MqttMessage
+import org.eclipse.paho.client.mqttv3.MqttException
+import org.eclipse.paho.client.mqttv3.MqttCallback
+import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken
+import org.eclipse.paho.client.mqttv3.persist.MqttDefaultFilePersistence
+import org.eclipse.paho.client.mqttv3.MqttConnectOptions
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.TimeUnit
+
+
+class SubscriberCallback implements MqttCallback {
+
+    int m_numReceived = 0
+    long m_startTime
+    boolean firstMessageReceived = false
+
+    private CountDownLatch m_latch = new CountDownLatch(1)
+
+    void waitFinish() {
+        m_latch.await()
+    }
+
+    public void connectionLost(Throwable cause) {
+        m_latch.countDown()
+    }
+
+    public void messageArrived(String topic, MqttMessage message) throws Exception {
+        //println "Received message ${new String(message.payload)} on topic [${topic}]"
+        if (!firstMessageReceived) {
+            m_startTime = System.currentTimeMillis()
+            firstMessageReceived = true
+        }
+        if (topic == "/exit") {
+            long stopTime = System.currentTimeMillis()
+            long spentTime = stopTime - m_startTime
+            println "/exit received"
+            println "subscriber disconnected, received ${m_numReceived} messages in ${spentTime} ms"
+            m_latch.countDown()
+        } else {
+            //println "-received ${message} on ${topic} with QoS ${message.qos}"
+            m_numReceived++
+        }
+    }
+
+    public void deliveryComplete(IMqttDeliveryToken token) {
+        //To change body of implemented methods use File | Settings | File Templates.
+    }
+}
+
+if (args.size() < 2) {
+    println "Usage subscriber <host> <QoS>"
+    return
+}
+
+String host = args[0]
+int qos = args[1] as int
+String tmpDir = System.getProperty("java.io.tmpdir")
+MqttDefaultFilePersistence dataStore = new MqttDefaultFilePersistence(tmpDir)
+
+int rnd = (Math.random() * 100) as int
+MqttClient client = new MqttClient("tcp://${host}:1883", "SubscriberClient${rnd}", dataStore)
+def callback = new SubscriberCallback()
+client.callback = callback
+//Only for Apollo ---
+//MqttConnectOptions connOptions = new MqttConnectOptions()
+//connOptions.userName ='admin'
+//connOptions.password = 'password' as char[]
+//client.connect(connOptions)
+//Only for Apollo ---
+client.connect()
+client.subscribe("topic", 0)
+println "subscribed to topic"
+client.subscribe("/exit", 0)
+println "subscribed to /exit"
+
+callback.waitFinish()
+client.diconnect()