diff --git a/sonoff/sonoff_post.h b/sonoff/sonoff_post.h
index 0143234b6..d488f4ea4 100644
--- a/sonoff/sonoff_post.h
+++ b/sonoff/sonoff_post.h
@@ -33,8 +33,10 @@ void WifiWpsStatusCallback(wps_cb_status status);
 }
 #endif
 
+//#ifdef USE_KNX  // Enabling this will fail compilation. It has no impact if not used. (20180417)
 #include <esp-knx-ip.h>
 void KNX_CB_Action(message_t const &msg, void *arg);
+//#endif  // USE_KNX
 
 #define USE_DHT                               // Default DHT11 sensor needs no external library