diff --git a/src/main/java/org/gcube/contentmanagement/blobstorage/transport/backend/MongoIOManager.java b/src/main/java/org/gcube/contentmanagement/blobstorage/transport/backend/MongoIOManager.java
index 86a8f32..190ad03 100644
--- a/src/main/java/org/gcube/contentmanagement/blobstorage/transport/backend/MongoIOManager.java
+++ b/src/main/java/org/gcube/contentmanagement/blobstorage/transport/backend/MongoIOManager.java
@@ -1067,11 +1067,11 @@ public class MongoIOManager {
 	public void close() {
 //		if(mongo!=null)
 //			mongo.close();
-		logger.debug(" try to close backend but the close operation is not implemented");
+		logger.debug(" cleaning mongo objects");
 //		logger.info("Mongo has been closed");
 //		mongo=null;
-//		gfs=null;
-//		db=null;
+		gfs=null;
+		db=null;
 	}
 	
 	
@@ -1079,6 +1079,8 @@ public class MongoIOManager {
 		if(mongo!=null)
 			mongo.close();
 		logger.info("Mongo pool closed");
+		close();
+		mongo=null;
 	}
 	
 	public void removeGFSFile(GridFSDBFile f, ObjectId idF){
diff --git a/src/main/java/org/gcube/contentmanagement/blobstorage/transport/backend/MongoOperationManager.java b/src/main/java/org/gcube/contentmanagement/blobstorage/transport/backend/MongoOperationManager.java
index f933acf..bd1940f 100644
--- a/src/main/java/org/gcube/contentmanagement/blobstorage/transport/backend/MongoOperationManager.java
+++ b/src/main/java/org/gcube/contentmanagement/blobstorage/transport/backend/MongoOperationManager.java
@@ -11,6 +11,7 @@ import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 
 import org.gcube.contentmanagement.blobstorage.resource.MemoryType;
 import org.gcube.contentmanagement.blobstorage.resource.RequestObject;
@@ -134,8 +135,10 @@ public class MongoOperationManager extends TransportManager{
 	}
 	
 	public void forceClose() {
-		mongoPrimaryInstance.forceClose();
-		mongoSecondaryInstance.forceClose();
+		if(Objects.nonNull(mongoPrimaryInstance))
+			mongoPrimaryInstance.forceClose();
+		if(Objects.nonNull(mongoSecondaryInstance))
+			mongoSecondaryInstance.forceClose();
 	}
 	
 	/**