diff --git a/parser/src/main/java/org/dna/mqtt/moquette/messaging/spi/impl/SimpleMessaging.java b/parser/src/main/java/org/dna/mqtt/moquette/messaging/spi/impl/SimpleMessaging.java
index b6e78d60..684d5b73 100644
--- a/parser/src/main/java/org/dna/mqtt/moquette/messaging/spi/impl/SimpleMessaging.java
+++ b/parser/src/main/java/org/dna/mqtt/moquette/messaging/spi/impl/SimpleMessaging.java
@@ -45,6 +45,7 @@ public class SimpleMessaging implements IMessaging {
         Subscription newSubscription = new Subscription(clientId, topic, qos);
         rwLock.writeLock().lock();
         if (subscriptions.contains(newSubscription)) {
+            rwLock.writeLock().unlock();
             return;
         }
         subscriptions.add(newSubscription);