diff --git a/libraries/AP_Compass/AP_Compass_SITL.h b/libraries/AP_Compass/AP_Compass_SITL.h
index e5e0c4c650..0678d4ffd6 100644
--- a/libraries/AP_Compass/AP_Compass_SITL.h
+++ b/libraries/AP_Compass/AP_Compass_SITL.h
@@ -9,7 +9,7 @@
 #include <AP_Math/AP_Math.h>
 #include <AP_Declination/AP_Declination.h>
 
-#define SITL_NUM_COMPASSES 2
+#define SITL_NUM_COMPASSES 3
 
 class AP_Compass_SITL : public AP_Compass_Backend {
 public: