Unsubscribre from previous snapshot plus update request

I am using the following code to try to unsubscribe from a previous snapshot plus update request (using quickfix/j), but the engine keeps disconnecting me without receiving response form the server. Is the server working correctly? Is it necessary to unsubscribe before closing the session with a logout message?

        quickfix.fix44.MarketDataRequest message = new quickfix.fix44.MarketDataRequest  (new MDReqID("REQUEST"+ nID), new SubscriptionRequestType(SubscriptionRequestType.DISABLE_PREVIOUS_SNAPSHOT_PLUS_UPDATE_REQUEST), new MarketDepth(1));            
        message.set(new MDUpdateType(1));            
        message.getHeader().setField(new StringField(50, "QUOTE"));            
        quickfix.fix44.MarketDataRequest.NoMDEntryTypes noMDEntryTypes = new quickfix.fix44.MarketDataRequest.NoMDEntryTypes();
        MDEntryType mdEntryType_bid = new MDEntryType('0');
        noMDEntryTypes.set(mdEntryType_bid);
        message.addGroup(noMDEntryTypes);
        MDEntryType mdEntryType_offer = new MDEntryType('1');
        noMDEntryTypes.set(mdEntryType_offer);
        message.addGroup(noMDEntryTypes);        
        quickfix.fix44.MarketDataRequest.NoRelatedSym relatedSymbol = new quickfix.fix44.MarketDataRequest.NoRelatedSym();
        relatedSymbol.set(new quickfix.fix44.component.Instrument(new Symbol("1")));            
        message.addGroup(relatedSymbol);