diff --git a/src/knx/bau27B0.h b/src/knx/bau27B0.h
index c2816b2..fdfa615 100644
--- a/src/knx/bau27B0.h
+++ b/src/knx/bau27B0.h
@@ -4,10 +4,8 @@
 #include "rf_medium_object.h"
 #include "rf_physical_layer.h"
 #include "rf_data_link_layer.h"
-#ifdef USE_CEMI_SERVER
 #include "cemi_server.h"
 #include "cemi_server_object.h"
-#endif
 
 class Bau27B0 : public BauSystemB
 {
diff --git a/src/knx/cemi_server.cpp b/src/knx/cemi_server.cpp
index 120c50a..7ee214d 100644
--- a/src/knx/cemi_server.cpp
+++ b/src/knx/cemi_server.cpp
@@ -1,3 +1,5 @@
+#ifdef USE_CEMI_SERVER
+
 #include "cemi_server.h"
 #include "cemi_frame.h"
 #include "bau_systemB.h"
@@ -346,3 +348,5 @@ void CemiServer::loop()
 {
     _usbTunnelInterface.loop();
 }
+
+#endif
diff --git a/src/knx/cemi_server_object.cpp b/src/knx/cemi_server_object.cpp
index 43a473d..5652820 100644
--- a/src/knx/cemi_server_object.cpp
+++ b/src/knx/cemi_server_object.cpp
@@ -1,3 +1,5 @@
+#ifdef USE_CEMI_SERVER
+
 #include <cstring>
 #include "cemi_server_object.h"
 #include "bits.h"
@@ -109,3 +111,5 @@ PropertyDescription* CemiServerObject::propertyDescriptions()
 {
     return _propertyDescriptions;
 }
+
+#endif
diff --git a/src/knx/cemi_server_object.h b/src/knx/cemi_server_object.h
index 18e22fe..971a740 100644
--- a/src/knx/cemi_server_object.h
+++ b/src/knx/cemi_server_object.h
@@ -21,4 +21,4 @@ private:
     uint8_t _addInfoTypesTable[1] = { 0x02 }; 
     uint8_t _commMode = 0x00;
 
-};
\ No newline at end of file
+};
diff --git a/src/knx/data_link_layer.cpp b/src/knx/data_link_layer.cpp
index 298bdff..05d2e48 100644
--- a/src/knx/data_link_layer.cpp
+++ b/src/knx/data_link_layer.cpp
@@ -12,6 +12,8 @@ DataLinkLayer::DataLinkLayer(DeviceObject& devObj, AddressTableObject& addrTab,
 {
 }
 
+#ifdef USE_CEMI_SERVER
+
 void DataLinkLayer::cemiServer(CemiServer& cemiServer)
 {
     _cemiServer = &cemiServer;
@@ -30,6 +32,7 @@ void DataLinkLayer::dataRequestFromTunnel(CemiFrame& frame)
     // Send to KNX medium
     sendFrame(frame);
 }
+#endif
 
 void DataLinkLayer::dataRequest(AckType ack, AddressType addrType, uint16_t destinationAddr, FrameFormat format, Priority priority, NPDU& npdu)
 {
@@ -60,16 +63,15 @@ void DataLinkLayer::dataConReceived(CemiFrame& frame, bool success)
     NPDU& npdu = frame.npdu();
     SystemBroadcast systemBroadcast = frame.systemBroadcast();
 
-    if (_cemiServer)
+#ifdef USE_CEMI_SERVER
+    // if the confirmation was caused by a tunnel request then
+    // do not send it to the local stack
+    if (frame.sourceAddress() == _cemiServer->clientAddress())
     {
-        // if the confirmation was caused by a tunnel request then
-        // do not send it to the local stack
-        if (frame.sourceAddress() == _cemiServer->clientAddress())
-        {
-            // Stop processing here and do NOT send it the local network layer
-            return;
-        }
+        // Stop processing here and do NOT send it the local network layer
+        return;
     }
+#endif    
 
     if (addrType == GroupAddress && destination == 0)
             if (systemBroadcast == SysBroadcast)
@@ -94,15 +96,14 @@ void DataLinkLayer::frameRecieved(CemiFrame& frame)
     uint16_t ownAddr = _deviceObject.induvidualAddress();
     SystemBroadcast systemBroadcast = frame.systemBroadcast();
 
-    if (_cemiServer)
+#ifdef USE_CEMI_SERVER
+    // Do not send our own message back to the tunnel
+    if (frame.sourceAddress() != _cemiServer->clientAddress())
     {
-        // Do not send our own message back to the tunnel
-        if (frame.sourceAddress() != _cemiServer->clientAddress())
-        {
-            _cemiServer->dataIndicationToTunnel(frame);
-        }
+        _cemiServer->dataIndicationToTunnel(frame);
     }
-    
+#endif
+
     if (source == ownAddr)
         _deviceObject.induvidualAddressDuplication(true);
 
@@ -166,18 +167,17 @@ bool DataLinkLayer::sendTelegram(NPDU & npdu, AckType ack, uint16_t destinationA
     // Thus, reuse the modified cEMI frame as "frame" is only passed by reference here!
     bool success = sendFrame(frame);
 
-    if (_cemiServer)
-    {
-        CemiFrame tmpFrame(frame.data(), frame.totalLenght());
-        // We can just copy the pointer for rfSerialOrDoA as sendFrame() sets
-        // a pointer to const uint8_t data in either device object (serial) or
-        // RF medium object (domain address)
-        tmpFrame.rfSerialOrDoA(frame.rfSerialOrDoA()); 
-        tmpFrame.rfInfo(frame.rfInfo());
-        tmpFrame.rfLfn(frame.rfLfn());
-        tmpFrame.confirm(ConfirmNoError);
-        _cemiServer->dataIndicationToTunnel(tmpFrame);
-    }
+#ifdef USE_CEMI_SERVER
+    CemiFrame tmpFrame(frame.data(), frame.totalLenght());
+    // We can just copy the pointer for rfSerialOrDoA as sendFrame() sets
+    // a pointer to const uint8_t data in either device object (serial) or
+    // RF medium object (domain address)
+    tmpFrame.rfSerialOrDoA(frame.rfSerialOrDoA()); 
+    tmpFrame.rfInfo(frame.rfInfo());
+    tmpFrame.rfLfn(frame.rfLfn());
+    tmpFrame.confirm(ConfirmNoError);
+    _cemiServer->dataIndicationToTunnel(tmpFrame);
+#endif
 
     return success;
 }
diff --git a/src/knx/data_link_layer.h b/src/knx/data_link_layer.h
index 0ae948b..770e943 100644
--- a/src/knx/data_link_layer.h
+++ b/src/knx/data_link_layer.h
@@ -13,9 +13,11 @@ class DataLinkLayer
     DataLinkLayer(DeviceObject& devObj, AddressTableObject& addrTab, NetworkLayer& layer,
                   Platform& platform);
 
+#ifdef USE_CEMI_SERVER
     // from tunnel
     void cemiServer(CemiServer& cemiServer);
     void dataRequestFromTunnel(CemiFrame& frame);
+#endif
 
     // from network layer
     void dataRequest(AckType ack, AddressType addrType, uint16_t destinationAddr, FrameFormat format,
@@ -35,5 +37,7 @@ class DataLinkLayer
     AddressTableObject& _groupAddressTable;
     NetworkLayer& _networkLayer;
     Platform& _platform;
+#ifdef USE_CEMI_SERVER
     CemiServer* _cemiServer;
+#endif    
 };
diff --git a/src/knx/usb_tunnel_interface.cpp b/src/knx/usb_tunnel_interface.cpp
index 4ce0fa5..11019a7 100644
--- a/src/knx/usb_tunnel_interface.cpp
+++ b/src/knx/usb_tunnel_interface.cpp
@@ -1,3 +1,5 @@
+#ifdef USE_CEMI_SERVER
+
 #include "bits.h"
 #include "usb_tunnel_interface.h"
 #include "cemi_server.h"
@@ -537,3 +539,5 @@ uint16_t UsbTunnelInterface::getHidReportDescriptorLength()
 {
 	return sizeof(descHidReport);
 }
+
+#endif