diff --git a/SensorGroup.cpp b/SensorGroup.cpp
index 92fc64b..02dd5ce 100644
--- a/SensorGroup.cpp
+++ b/SensorGroup.cpp
@@ -9,6 +9,7 @@ void SensorGroup::checkAll() {
 
 // called by command to get sensor list   
 void SensorGroup::printAll(Print * serial) {
+    (void)serial; // suppress unused warning
     #ifdef EXRAIL_ACTIVE
     doExrailSensorGroup(GroupProcess::PRINT,serial);
     #endif
diff --git a/Sensors.h b/Sensors.h
index f0eded5..c1550e0 100644
--- a/Sensors.h
+++ b/Sensors.h
@@ -24,6 +24,7 @@
 
 #include "Arduino.h"
 #include "IODevice.h"
+#include "SensorGroup.h"
 
 // Uncomment the following #define statement to use callback notification
 //  where the driver supports it.