diff --git a/conf/autopilot/subsystems/rotorcraft/fdm_nps.makefile b/conf/autopilot/subsystems/rotorcraft/fdm_nps.makefile
index 51e0e4c1ce..fec5b73817 100644
--- a/conf/autopilot/subsystems/rotorcraft/fdm_nps.makefile
+++ b/conf/autopilot/subsystems/rotorcraft/fdm_nps.makefile
@@ -17,7 +17,7 @@ NPSDIR = $(SIMDIR)/nps
 
 sim.ARCHDIR = $(ARCH)
 
-sim.CFLAGS  += -DSITL -DNPS
+sim.CFLAGS  += -DSITL -DUSE_NPS
 sim.CFLAGS  += `pkg-config glib-2.0 --cflags` -I /usr/include/meschach
 sim.LDFLAGS += `pkg-config glib-2.0 --libs` -lm -lpcre -lglibivy -lgsl -lgslcblas
 sim.CFLAGS  += -I$(NPSDIR) -I$(SRC_FIRMWARE) -I$(SRC_BOARD) -I../simulator -I$(PAPARAZZI_HOME)/conf/simulator/nps
diff --git a/sw/airborne/arch/sim/subsystems/imu/imu_b2_arch.c b/sw/airborne/arch/sim/subsystems/imu/imu_b2_arch.c
index e486ebbc38..e680ebc675 100644
--- a/sw/airborne/arch/sim/subsystems/imu/imu_b2_arch.c
+++ b/sw/airborne/arch/sim/subsystems/imu/imu_b2_arch.c
@@ -35,6 +35,7 @@ void imu_periodic(void) {
 
 }
 
+#ifdef USE_NPS
 #include "nps_sensors.h"
 
 void imu_feed_gyro_accel(void) {
@@ -61,3 +62,4 @@ void imu_feed_mag(void) {
   ami601_status = AMI601_DATA_AVAILABLE;
 #endif
 }
+#endif //USE_NPS
diff --git a/sw/airborne/arch/sim/subsystems/imu/imu_b2_arch.h b/sw/airborne/arch/sim/subsystems/imu/imu_b2_arch.h
index 8ef38139af..025acd33bf 100644
--- a/sw/airborne/arch/sim/subsystems/imu/imu_b2_arch.h
+++ b/sw/airborne/arch/sim/subsystems/imu/imu_b2_arch.h
@@ -31,8 +31,9 @@
 
 extern int imu_overrun;
 
+#ifdef USE_NPS
 extern void imu_feed_gyro_accel(void);
 extern void imu_feed_mag(void);
-
+#endif
 
 #endif /* IMU_B2_HW_H */
diff --git a/sw/airborne/arch/sim/subsystems/radio_control/ppm_arch.c b/sw/airborne/arch/sim/subsystems/radio_control/ppm_arch.c
index de1a37d3d7..be462fc82b 100644
--- a/sw/airborne/arch/sim/subsystems/radio_control/ppm_arch.c
+++ b/sw/airborne/arch/sim/subsystems/radio_control/ppm_arch.c
@@ -28,7 +28,7 @@
 #include <inttypes.h>
 #include <caml/mlvalues.h>
 
-#ifdef NPS
+#ifdef USE_NPS
 #include "nps_radio_control.h"
 #endif
 
@@ -55,7 +55,7 @@ value send_ppm(value unit) {
   return unit;
 }
 
-#ifdef NPS
+#ifdef USE_NPS
 #define PPM_OF_NPS(_nps, _neutral, _min, _max)                          \
   ((_nps) >= 0 ? (_neutral) + (_nps) * ((_max)-(_neutral)) : (_neutral) + (_nps) * ((_neutral)- (_min)))
 
@@ -94,7 +94,7 @@ value send_ppm(value unit) {
   return unit;
 }
 
-#ifdef NPS
+#ifdef USE_NPS
 void radio_control_feed(void) {}
 #endif
 
diff --git a/sw/airborne/arch/sim/subsystems/radio_control/ppm_arch.h b/sw/airborne/arch/sim/subsystems/radio_control/ppm_arch.h
index 5f9bfd681d..c0f27a3b5e 100644
--- a/sw/airborne/arch/sim/subsystems/radio_control/ppm_arch.h
+++ b/sw/airborne/arch/sim/subsystems/radio_control/ppm_arch.h
@@ -36,7 +36,7 @@
 
 #define PPM_NB_CHANNEL RADIO_CONTROL_NB_CHANNEL
 
-#ifdef NPS
+#ifdef USE_NPS
 extern void radio_control_feed(void);
 #endif