diff --git a/sw/airborne/arch/sim/subsystems/imu/imu_aspirin_arch.c b/sw/airborne/arch/sim/subsystems/imu/imu_aspirin_arch.c
index 383dd78880..7b334860ec 100644
--- a/sw/airborne/arch/sim/subsystems/imu/imu_aspirin_arch.c
+++ b/sw/airborne/arch/sim/subsystems/imu/imu_aspirin_arch.c
@@ -33,6 +33,7 @@ void imu_periodic(void) {
 
 }
 
+#if USE_NPS
 #include "nps_sensors.h"
 
 void imu_feed_gyro_accel(void) {
@@ -56,3 +57,4 @@ void imu_feed_mag(void) {
   hmc5843.data.value[IMU_MAG_Z_CHAN] = sensors.mag.value.z;
   hmc5843.data_available = TRUE;
 }
+#endif
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 e680ebc675..deb32021cb 100644
--- a/sw/airborne/arch/sim/subsystems/imu/imu_b2_arch.c
+++ b/sw/airborne/arch/sim/subsystems/imu/imu_b2_arch.c
@@ -35,7 +35,7 @@ void imu_periodic(void) {
 
 }
 
-#ifdef USE_NPS
+#if USE_NPS
 #include "nps_sensors.h"
 
 void imu_feed_gyro_accel(void) {
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 025acd33bf..2944460181 100644
--- a/sw/airborne/arch/sim/subsystems/imu/imu_b2_arch.h
+++ b/sw/airborne/arch/sim/subsystems/imu/imu_b2_arch.h
@@ -31,7 +31,7 @@
 
 extern int imu_overrun;
 
-#ifdef USE_NPS
+#if USE_NPS
 extern void imu_feed_gyro_accel(void);
 extern void imu_feed_mag(void);
 #endif
diff --git a/sw/airborne/arch/sim/subsystems/imu/imu_crista_arch.c b/sw/airborne/arch/sim/subsystems/imu/imu_crista_arch.c
index ee07d78462..4d78cef36a 100644
--- a/sw/airborne/arch/sim/subsystems/imu/imu_crista_arch.c
+++ b/sw/airborne/arch/sim/subsystems/imu/imu_crista_arch.c
@@ -10,7 +10,7 @@ void imu_crista_arch_init(void) {
 
 }
 
-
+#if USE_NPS
 #include "nps_sensors.h"
 
 void imu_feed_gyro_accel(void) {
@@ -29,3 +29,4 @@ void imu_feed_mag(void) {
   ami601_values[IMU_MAG_Z_CHAN] = sensors.mag.value.z;
   ami601_status = AMI601_DATA_AVAILABLE;
 }
+#endif
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 be462fc82b..164a296e45 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 USE_NPS
+#if USE_NPS
 #include "nps_radio_control.h"
 #endif
 
@@ -55,7 +55,7 @@ value send_ppm(value unit) {
   return unit;
 }
 
-#ifdef USE_NPS
+#if 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 USE_NPS
+#if 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 c0f27a3b5e..5a6bcbe639 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 USE_NPS
+#if USE_NPS
 extern void radio_control_feed(void);
 #endif