diff --git a/CommandStation-EX.ino b/CommandStation-EX.ino
index 57a178b..0cbf056 100644
--- a/CommandStation-EX.ino
+++ b/CommandStation-EX.ino
@@ -18,6 +18,9 @@
 
 #if __has_include ( "config.h")
   #include "config.h"
+  #ifndef MOTOR_SHIELD_TYPE
+  #error Your config.h must include a MOTOR_SHIELD_TYPE definition. If you see this warning in spite not having a config.h, you have a buggy preprocessor and must copy config.example.h to config.h
+  #endif
 #else
   #warning config.h not found. Using defaults from config.example.h
   #include "config.example.h"