diff --git a/libraries/AP_HAL/SIMState.h b/libraries/AP_HAL/SIMState.h
index b86c0282d4..af62741110 100644
--- a/libraries/AP_HAL/SIMState.h
+++ b/libraries/AP_HAL/SIMState.h
@@ -33,6 +33,8 @@
 #include <SITL/SIM_AIS.h>
 #include <SITL/SIM_GPS.h>
 
+#include <SITL/SIM_EFI_Hirth.h>
+
 #include <SITL/SIM_Frsky_D.h>
 #include <SITL/SIM_CRSF.h>
 #include <SITL/SIM_PS_RPLidarA2.h>
@@ -206,6 +208,9 @@ private:
     // simulated EFI MegaSquirt device:
     SITL::EFI_MegaSquirt *efi_ms;
 
+    // simulated EFI Hirth device:
+    SITL::EFI_Hirth *efi_hirth;
+
 #if CONFIG_HAL_BOARD == HAL_BOARD_SITL
     // output socket for flightgear viewing
     SocketAPM fg_socket{true};