diff --git a/platforms/nuttx/src/px4/nxp/kinetis/tone_alarm/ToneAlarmInterface.cpp b/platforms/nuttx/src/px4/nxp/kinetis/tone_alarm/ToneAlarmInterface.cpp
index e9df8ccf92..df36cd725c 100644
--- a/platforms/nuttx/src/px4/nxp/kinetis/tone_alarm/ToneAlarmInterface.cpp
+++ b/platforms/nuttx/src/px4/nxp/kinetis/tone_alarm/ToneAlarmInterface.cpp
@@ -43,7 +43,7 @@
 #include <px4_platform_common/defines.h>
 #include <systemlib/px4_macros.h>
 
-#include <cmath>
+#include <math.h>
 
 #define CAT3_(A, B, C)    A##B##C
 #define CAT3(A, B, C)     CAT3_(A, B, C)
@@ -166,7 +166,7 @@ void start_note(unsigned frequency)
 	float signal_period = (1.0f / frequency) * 0.5f;
 
 	// Calculate the hardware clock divisor rounded to the nearest integer.
-	unsigned int divisor = std::round(signal_period * TONE_ALARM_CLOCK);
+	unsigned int divisor = roundf(signal_period * TONE_ALARM_CLOCK);
 
 	rCNT = 0;
 	rMOD = divisor;        // Load new signal switching period.
diff --git a/platforms/nuttx/src/px4/stm/stm32_common/tone_alarm/ToneAlarmInterfacePWM.cpp b/platforms/nuttx/src/px4/stm/stm32_common/tone_alarm/ToneAlarmInterfacePWM.cpp
index cf07376ede..6ba13e65ac 100644
--- a/platforms/nuttx/src/px4/stm/stm32_common/tone_alarm/ToneAlarmInterfacePWM.cpp
+++ b/platforms/nuttx/src/px4/stm/stm32_common/tone_alarm/ToneAlarmInterfacePWM.cpp
@@ -34,7 +34,7 @@
 #include <drivers/device/device.h>
 #include <drivers/drv_tone_alarm.h>
 #include <px4_platform_common/defines.h>
-#include <cmath>
+#include <math.h>
 
 /* Check that tone alarm and HRT timers are different */
 #if defined(TONE_ALARM_TIMER) && defined(HRT_TIMER)
@@ -288,7 +288,7 @@ void start_note(unsigned frequency)
 	float signal_period = (1.0f / frequency) * 0.5f;
 
 	// Calculate the hardware clock divisor rounded to the nearest integer.
-	unsigned int divisor = std::round(signal_period * TONE_ALARM_CLOCK);
+	unsigned int divisor = roundf(signal_period * TONE_ALARM_CLOCK);
 
 	// Pick the lowest prescaler value that we can use.
 	// (Note that the effective prescale value is 1 greater.)
diff --git a/src/drivers/linux_pwm_out/linux_pwm_out.cpp b/src/drivers/linux_pwm_out/linux_pwm_out.cpp
index 603ac9c87b..482c376194 100644
--- a/src/drivers/linux_pwm_out/linux_pwm_out.cpp
+++ b/src/drivers/linux_pwm_out/linux_pwm_out.cpp
@@ -36,7 +36,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include <cmath>
+#include <math.h>
 
 #include <px4_platform_common/tasks.h>
 #include <px4_platform_common/getopt.h>
diff --git a/src/drivers/snapdragon_pwm_out/snapdragon_pwm_out.cpp b/src/drivers/snapdragon_pwm_out/snapdragon_pwm_out.cpp
index a871ded4d6..6a600339f2 100644
--- a/src/drivers/snapdragon_pwm_out/snapdragon_pwm_out.cpp
+++ b/src/drivers/snapdragon_pwm_out/snapdragon_pwm_out.cpp
@@ -37,7 +37,7 @@
 #include <px4_platform_common/getopt.h>
 #include <px4_platform_common/posix.h>
 #include <errno.h>
-#include <cmath>	// NAN
+#include <math.h>	// NAN
 #include <string.h>
 
 #include <uORB/Subscription.hpp>
diff --git a/src/drivers/tap_esc/tap_esc.cpp b/src/drivers/tap_esc/tap_esc.cpp
index 911be2bb0a..fe50925929 100644
--- a/src/drivers/tap_esc/tap_esc.cpp
+++ b/src/drivers/tap_esc/tap_esc.cpp
@@ -40,7 +40,7 @@
 #include <px4_platform_common/posix.h>
 #include <errno.h>
 
-#include <cmath>	// NAN
+#include <math.h>	// NAN
 #include <cstring>
 
 #include <lib/mathlib/mathlib.h>
diff --git a/src/drivers/uavcan/sensors/baro.cpp b/src/drivers/uavcan/sensors/baro.cpp
index 6a515a6a55..22236e9e1f 100644
--- a/src/drivers/uavcan/sensors/baro.cpp
+++ b/src/drivers/uavcan/sensors/baro.cpp
@@ -37,7 +37,7 @@
 
 #include <drivers/drv_hrt.h>
 #include "baro.hpp"
-#include <cmath>
+#include <math.h>
 
 const char *const UavcanBarometerBridge::NAME = "baro";
 
diff --git a/src/drivers/uavcan/uavcan_drivers/kinetis/driver/src/uc_kinetis_clock.cpp b/src/drivers/uavcan/uavcan_drivers/kinetis/driver/src/uc_kinetis_clock.cpp
index fd57f8b39f..9560284094 100644
--- a/src/drivers/uavcan/uavcan_drivers/kinetis/driver/src/uc_kinetis_clock.cpp
+++ b/src/drivers/uavcan/uavcan_drivers/kinetis/driver/src/uc_kinetis_clock.cpp
@@ -9,7 +9,7 @@
 
 #if UAVCAN_KINETIS_TIMER_NUMBER
 # include <cassert>
-# include <cmath>
+# include <math.h>
 
 /*
  * Timer instance
diff --git a/src/drivers/uavcan/uavcan_drivers/stm32/driver/src/uc_stm32_clock.cpp b/src/drivers/uavcan/uavcan_drivers/stm32/driver/src/uc_stm32_clock.cpp
index 3e4fb715c7..c2e0216ea2 100644
--- a/src/drivers/uavcan/uavcan_drivers/stm32/driver/src/uc_stm32_clock.cpp
+++ b/src/drivers/uavcan/uavcan_drivers/stm32/driver/src/uc_stm32_clock.cpp
@@ -9,7 +9,7 @@
 #if UAVCAN_STM32_TIMER_NUMBER
 
 #include <cassert>
-#include <cmath>
+#include <math.h>
 
 /*
  * Timer instance
diff --git a/src/lib/mathlib/math/filter/LowPassFilter2p.cpp b/src/lib/mathlib/math/filter/LowPassFilter2p.cpp
index 2be5227a90..55e8cdc513 100644
--- a/src/lib/mathlib/math/filter/LowPassFilter2p.cpp
+++ b/src/lib/mathlib/math/filter/LowPassFilter2p.cpp
@@ -35,7 +35,7 @@
 
 #include <px4_platform_common/defines.h>
 
-#include <cmath>
+#include <math.h>
 
 namespace math
 {
diff --git a/src/lib/mathlib/math/filter/LowPassFilter2pVector3f.cpp b/src/lib/mathlib/math/filter/LowPassFilter2pVector3f.cpp
index fb4845d19a..1619d4564d 100644
--- a/src/lib/mathlib/math/filter/LowPassFilter2pVector3f.cpp
+++ b/src/lib/mathlib/math/filter/LowPassFilter2pVector3f.cpp
@@ -35,7 +35,7 @@
 
 #include <px4_platform_common/defines.h>
 
-#include <cmath>
+#include <math.h>
 
 namespace math
 {
diff --git a/src/lib/mixer/MultirotorMixer/test_mixer_multirotor.cpp b/src/lib/mixer/MultirotorMixer/test_mixer_multirotor.cpp
index 46af77012f..87a1ebc3ed 100644
--- a/src/lib/mixer/MultirotorMixer/test_mixer_multirotor.cpp
+++ b/src/lib/mixer/MultirotorMixer/test_mixer_multirotor.cpp
@@ -39,7 +39,7 @@
 #include "MultirotorMixer.hpp"
 
 #include <cstdio>
-#include <cmath>
+#include <math.h>
 
 static const unsigned output_max = 16;
 static float actuator_controls[output_max] {};
diff --git a/src/modules/commander/Commander.cpp b/src/modules/commander/Commander.cpp
index 09f9b64363..811e24952b 100644
--- a/src/modules/commander/Commander.cpp
+++ b/src/modules/commander/Commander.cpp
@@ -76,7 +76,7 @@
 #include <circuit_breaker/circuit_breaker.h>
 #include <systemlib/mavlink_log.h>
 
-#include <cmath>
+#include <math.h>
 #include <float.h>
 #include <cstring>
 
@@ -768,7 +768,7 @@ Commander::handle_command(vehicle_status_s *status_local, const vehicle_command_
 				bool cmd_arms = (static_cast<int>(cmd.param1 + 0.5f) == 1);
 
 				// Arm/disarm is enforced when param2 is set to a magic number.
-				const bool enforce = (static_cast<int>(std::round(cmd.param2)) == 21196);
+				const bool enforce = (static_cast<int>(roundf(cmd.param2)) == 21196);
 
 				if (!enforce) {
 					if (!land_detector.landed && !is_ground_rover(&status)) {
diff --git a/src/modules/commander/airspeed_calibration.cpp b/src/modules/commander/airspeed_calibration.cpp
index 21e1cd9861..98f816b48a 100644
--- a/src/modules/commander/airspeed_calibration.cpp
+++ b/src/modules/commander/airspeed_calibration.cpp
@@ -48,7 +48,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <poll.h>
-#include <cmath>
+#include <math.h>
 #include <drivers/drv_hrt.h>
 #include <drivers/drv_airspeed.h>
 #include <uORB/topics/differential_pressure.h>
diff --git a/src/modules/commander/gyro_calibration.cpp b/src/modules/commander/gyro_calibration.cpp
index ed4f18b9c4..1d28f5aad8 100644
--- a/src/modules/commander/gyro_calibration.cpp
+++ b/src/modules/commander/gyro_calibration.cpp
@@ -50,7 +50,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <poll.h>
-#include <cmath>
+#include <math.h>
 #include <string.h>
 #include <drivers/drv_hrt.h>
 #include <uORB/topics/sensor_combined.h>
diff --git a/src/modules/commander/mag_calibration.cpp b/src/modules/commander/mag_calibration.cpp
index a1a7355cf4..cbd1592178 100644
--- a/src/modules/commander/mag_calibration.cpp
+++ b/src/modules/commander/mag_calibration.cpp
@@ -50,7 +50,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <poll.h>
-#include <cmath>
+#include <math.h>
 #include <fcntl.h>
 #include <drivers/drv_hrt.h>
 #include <drivers/drv_accel.h>
diff --git a/src/modules/land_detector/MulticopterLandDetector.cpp b/src/modules/land_detector/MulticopterLandDetector.cpp
index 96a78c3fd8..e682753aab 100644
--- a/src/modules/land_detector/MulticopterLandDetector.cpp
+++ b/src/modules/land_detector/MulticopterLandDetector.cpp
@@ -61,7 +61,7 @@
  * @author Julian Oes <julian@oes.ch>
  */
 
-#include <cmath>
+#include <math.h>
 #include <mathlib/mathlib.h>
 #include <matrix/math.hpp>
 
diff --git a/src/modules/mavlink/mavlink_mission.cpp b/src/modules/mavlink/mavlink_mission.cpp
index 857ec0aa2f..12ba2f6b53 100644
--- a/src/modules/mavlink/mavlink_mission.cpp
+++ b/src/modules/mavlink/mavlink_mission.cpp
@@ -1546,8 +1546,8 @@ MavlinkMissionManager::format_mavlink_mission_item(const struct mission_item_s *
 			mavlink_mission_item_int_t *item_int =
 				reinterpret_cast<mavlink_mission_item_int_t *>(mavlink_mission_item);
 
-			item_int->x = std::round(mission_item->lat * 1e7);
-			item_int->y = std::round(mission_item->lon * 1e7);
+			item_int->x = round(mission_item->lat * 1e7);
+			item_int->y = round(mission_item->lon * 1e7);
 
 		} else {
 			mavlink_mission_item->x = (float)mission_item->lat;