diff --git a/libraries/SITL/SITL.h b/libraries/SITL/SITL.h
index 54a610905c..04f3d20e93 100644
--- a/libraries/SITL/SITL.h
+++ b/libraries/SITL/SITL.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <AP_Math/AP_Math.h>
 #include <GCS_MAVLink/GCS_MAVLink.h>
 
 class DataFlash_Class;