diff --git a/libraries/AP_AHRS/AP_AHRS.h b/libraries/AP_AHRS/AP_AHRS.h
index a91e6dde25..ddae5e3003 100644
--- a/libraries/AP_AHRS/AP_AHRS.h
+++ b/libraries/AP_AHRS/AP_AHRS.h
@@ -21,22 +21,10 @@
  *
  */
 
-#include <AP_HAL/AP_HAL_Boards.h>
+#include "AP_AHRS_config.h"
+
 #include <AP_HAL/Semaphores.h>
 
-#ifndef HAL_NAVEKF2_AVAILABLE
-// only default to EK2 enabled on boards with over 1M flash
-#define HAL_NAVEKF2_AVAILABLE (BOARD_FLASH_SIZE>1024)
-#endif
-
-#ifndef HAL_NAVEKF3_AVAILABLE
-#define HAL_NAVEKF3_AVAILABLE 1
-#endif
-
-#ifndef AP_AHRS_SIM_ENABLED
-#define AP_AHRS_SIM_ENABLED AP_SIM_ENABLED
-#endif
-
 #if AP_AHRS_SIM_ENABLED
 #include <SITL/SITL.h>
 #endif
diff --git a/libraries/AP_AHRS/AP_AHRS_config.h b/libraries/AP_AHRS/AP_AHRS_config.h
new file mode 100644
index 0000000000..e600487d1d
--- /dev/null
+++ b/libraries/AP_AHRS/AP_AHRS_config.h
@@ -0,0 +1,16 @@
+#pragma once
+
+#include <AP_HAL/AP_HAL_Boards.h>
+
+#ifndef HAL_NAVEKF2_AVAILABLE
+// only default to EK2 enabled on boards with over 1M flash
+#define HAL_NAVEKF2_AVAILABLE (BOARD_FLASH_SIZE>1024)
+#endif
+
+#ifndef HAL_NAVEKF3_AVAILABLE
+#define HAL_NAVEKF3_AVAILABLE 1
+#endif
+
+#ifndef AP_AHRS_SIM_ENABLED
+#define AP_AHRS_SIM_ENABLED AP_SIM_ENABLED
+#endif