diff --git a/ArduCopterMega/defines.h b/ArduCopterMega/defines.h
index 4f4f448e14..049d634053 100644
--- a/ArduCopterMega/defines.h
+++ b/ArduCopterMega/defines.h
@@ -53,6 +53,8 @@
 
 #define MAX_SERVO_OUTPUT 2700
 
+#define SONAR 0
+#define BARO 1
 
 #define WP_START_BYTE 0x130	// where in memory home WP is stored + all other WP
 #define WP_SIZE 14