diff --git a/conf/firmwares/subsystems/rotorcraft/gps_sim_hitl.makefile b/conf/firmwares/subsystems/rotorcraft/gps_sim_hitl.makefile
index c2ea1367a8..5bfb1ca832 100644
--- a/conf/firmwares/subsystems/rotorcraft/gps_sim_hitl.makefile
+++ b/conf/firmwares/subsystems/rotorcraft/gps_sim_hitl.makefile
@@ -1,9 +1,10 @@
 # Hey Emacs, this is a -*- makefile -*-
 
-ap.srcs += $(SRC_SUBSYSTEMS)/gps.c
-ap.CFLAGS += -DGPS_TYPE_H=\"subsystems/gps/gps_sim_hitl.h\"
-ap.srcs += $(SRC_SUBSYSTEMS)/gps/gps_sim_hitl.c
 ap.CFLAGS += -DUSE_GPS -DHITL
+ap.CFLAGS += -DPRIMARY_GPS_TYPE=\"subsystems/gps/gps_sim_hitl.h\"
+ap.srcs += $(SRC_SUBSYSTEMS)/gps/gps_sim_hitl.c
+
+ap.srcs += $(SRC_SUBSYSTEMS)/gps.c
 
 ifneq ($(GPS_LED),none)
   ap.CFLAGS += -DGPS_LED=$(GPS_LED)
@@ -11,5 +12,5 @@ endif
 
 nps.CFLAGS += -DUSE_GPS
 nps.srcs += $(SRC_SUBSYSTEMS)/gps.c
-nps.CFLAGS += -DGPS_TYPE_H=\"subsystems/gps/gps_sim_nps.h\"
+nps.CFLAGS += -DPRIMARY_GPS_TYPE=\"subsystems/gps/gps_sim_nps.h\"
 nps.srcs += $(SRC_SUBSYSTEMS)/gps/gps_sim_nps.c
diff --git a/sw/airborne/subsystems/gps/gps_sim_hitl.c b/sw/airborne/subsystems/gps/gps_sim_hitl.c
index 96c563538a..8f695ac953 100644
--- a/sw/airborne/subsystems/gps/gps_sim_hitl.c
+++ b/sw/airborne/subsystems/gps/gps_sim_hitl.c
@@ -24,6 +24,7 @@
  * GPS subsystem simulation from rotorcrafts horizontal/vertical reference system
  */
 
+#include "subsystems/gps/gps_sim_hitl.h"
 #include "subsystems/gps.h"
 #include "subsystems/abi.h"
 
@@ -35,12 +36,12 @@
 bool_t gps_available;
 uint32_t gps_sim_hitl_timer;
 
-void gps_impl_init(void)
+void sim_hitl_gps_impl_init(void)
 {
   gps.fix = GPS_FIX_NONE;
 }
 
-void gps_sim_hitl_event(void)
+void sim_hitl_gps_event(void)
 {
   if (SysTimeTimer(gps_sim_hitl_timer) > 100000) {
     SysTimeTimerStart(gps_sim_hitl_timer);
@@ -93,3 +94,11 @@ void gps_sim_hitl_event(void)
     AbiSendMsgGPS(GPS_SIM_ID, now_ts, &gps);
   }
 }
+
+/*
+ * register callbacks & structs
+ */
+void sim_hitl_gps_register(void)
+{
+  gps_register_impl(sim_hitl_gps_impl_init, sim_hitl_gps_event, GPS_SIM_ID, 0);
+}
diff --git a/sw/airborne/subsystems/gps/gps_sim_hitl.h b/sw/airborne/subsystems/gps/gps_sim_hitl.h
index 84f4c6e145..9e27f78752 100644
--- a/sw/airborne/subsystems/gps/gps_sim_hitl.h
+++ b/sw/airborne/subsystems/gps/gps_sim_hitl.h
@@ -27,10 +27,14 @@
 #ifndef GPS_SIM_HITL_H
 #define GPS_SIM_HITL_H
 
-#include "std.h"
+#ifndef PrimaryGpsImpl
+#define PrimaryGpsImpl sim_hitl
+#endif
 
-extern void gps_sim_hitl_event(void);
+extern void sim_hitl_gps_event(void);
+extern void sim_hitl_gps_impl_init(void);
+extern void sim_hitl_gps_register(void);
 
-#define GpsEvent gps_sim_hitl_event
+// #define GpsEvent gps_sim_hitl_event
 
 #endif /* GPS_SIM_HITL_H */