diff --git a/broker/src/main/java/org/dna/mqtt/moquette/messaging/spi/impl/MemoryStorageService.java b/broker/src/main/java/org/dna/mqtt/moquette/messaging/spi/impl/MemoryStorageService.java
index 29300c68..e29157a1 100644
--- a/broker/src/main/java/org/dna/mqtt/moquette/messaging/spi/impl/MemoryStorageService.java
+++ b/broker/src/main/java/org/dna/mqtt/moquette/messaging/spi/impl/MemoryStorageService.java
@@ -8,13 +8,11 @@ import org.dna.mqtt.moquette.messaging.spi.impl.subscriptions.Subscription;
 import org.dna.mqtt.moquette.proto.messages.AbstractMessage;
 
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import org.dna.mqtt.moquette.messaging.spi.impl.HawtDBStorageService;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;