diff --git a/amperfied/connecthomediscovery.cpp b/amperfied/connecthomediscovery.cpp
index ed377b0..a8e90c4 100644
--- a/amperfied/connecthomediscovery.cpp
+++ b/amperfied/connecthomediscovery.cpp
@@ -85,6 +85,13 @@ void ConnectHomeDiscovery::checkNetworkDevice(const NetworkDeviceInfo &networkDe
                 cleanupConnection(connection);
                 return;
             }
+
+            if (connection->version() < 0x100 || connection->version() > 0x2ff) {
+                qCInfo(dcAmperfied()) << "Skipping invalid/unsupported AMPERFIED version" << connection->version();
+                cleanupConnection(connection);
+                return;
+            }
+
             Result result;
             result.firmwareVersion = connection->version();
             result.networkDeviceInfo = networkDeviceInfo;
diff --git a/amperfied/integrationpluginamperfied.cpp b/amperfied/integrationpluginamperfied.cpp
index 02e2182..f6ff59c 100644
--- a/amperfied/integrationpluginamperfied.cpp
+++ b/amperfied/integrationpluginamperfied.cpp
@@ -44,8 +44,6 @@ IntegrationPluginAmperfied::IntegrationPluginAmperfied()
 
 void IntegrationPluginAmperfied::discoverThings(ThingDiscoveryInfo *info)
 {
-    hardwareManager()->modbusRtuResource();
-
     if (info->thingClassId() == energyControlThingClassId) {
         EnergyControlDiscovery *discovery = new EnergyControlDiscovery(hardwareManager()->modbusRtuResource(), info);
 
@@ -270,6 +268,11 @@ void IntegrationPluginAmperfied::setupRtuConnection(ThingSetupInfo *info)
 {
     Thing *thing = info->thing();
     ModbusRtuMaster *master = hardwareManager()->modbusRtuResource()->getModbusRtuMaster(thing->paramValue(energyControlThingRtuMasterParamTypeId).toUuid());
+    if (!master) {
+        qCWarning(dcAmperfied()) << "The Modbus Master is not available any more.";
+        info->finish(Thing::ThingErrorHardwareNotAvailable, QT_TR_NOOP("The modbus RTU connection is not available."));
+        return;
+    }
     quint16 slaveId = thing->paramValue(energyControlThingSlaveIdParamTypeId).toUInt();
     AmperfiedModbusRtuConnection *connection = new AmperfiedModbusRtuConnection(master, slaveId, thing);