diff --git a/libraries/SITL/SIM_Aircraft.h b/libraries/SITL/SIM_Aircraft.h
index 1c2c0ca00f..e3a40c2a54 100644
--- a/libraries/SITL/SIM_Aircraft.h
+++ b/libraries/SITL/SIM_Aircraft.h
@@ -18,6 +18,8 @@
 
 #pragma once
 
+#if AP_SIM_ENABLED
+
 #include <AP_Math/AP_Math.h>
 
 #include "SITL.h"
@@ -343,3 +345,5 @@ private:
 };
 
 } // namespace SITL
+
+#endif // AP_SIM_ENABLED
diff --git a/libraries/SITL/SIM_Frame.cpp b/libraries/SITL/SIM_Frame.cpp
index e84bd7f962..ded149d7f3 100644
--- a/libraries/SITL/SIM_Frame.cpp
+++ b/libraries/SITL/SIM_Frame.cpp
@@ -471,6 +471,7 @@ void Frame::parse_vector3(picojson::value val, const char* label, Vector3f &para
 /*
   initialise the frame
  */
+#if AP_SIM_ENABLED
 void Frame::init(const char *frame_str, Battery *_battery)
 {
     model = default_model;
@@ -671,3 +672,4 @@ void Frame::current_and_voltage(float &voltage, float &current)
         current += motors[i].get_current();
     }
 }
+#endif // AP_SIM_ENABLED
diff --git a/libraries/SITL/SIM_Frame.h b/libraries/SITL/SIM_Frame.h
index 7bb4f94f7c..060ede03a6 100644
--- a/libraries/SITL/SIM_Frame.h
+++ b/libraries/SITL/SIM_Frame.h
@@ -44,7 +44,7 @@ public:
           num_motors(_num_motors),
           motors(_motors) {}
 
-
+#if AP_SIM_ENABLED
     // find a frame by name
     static Frame *find_frame(const char *name);
     
@@ -56,7 +56,8 @@ public:
                           const struct sitl_input &input,
                           Vector3f &rot_accel, Vector3f &body_accel, float* rpm,
                           bool use_drag=true);
-    
+#endif // AP_SIM_ENABLED
+
     float terminal_velocity;
     float terminal_rotation_rate;
     uint8_t motor_offset;
@@ -147,8 +148,10 @@ private:
     float areaCd;
     float mass;
     float thrust_max;
-    Battery *battery;
     float last_param_voltage;
+#if AP_SIM_ENABLED
+    Battery *battery;
+#endif
 
     // get air density in kg/m^3
     float get_air_density(float alt_amsl) const;
diff --git a/libraries/SITL/SIM_Motor.h b/libraries/SITL/SIM_Motor.h
index cdc4ffc71d..a12b235780 100644
--- a/libraries/SITL/SIM_Motor.h
+++ b/libraries/SITL/SIM_Motor.h
@@ -19,6 +19,7 @@
 #pragma once
 
 #include "SIM_Aircraft.h"
+#include <AP_Math/AP_Math.h>
 
 namespace SITL {