diff --git a/ArduSub/Attitude.cpp b/ArduSub/Attitude.cpp
index c8d68f6765..828f57798c 100644
--- a/ArduSub/Attitude.cpp
+++ b/ArduSub/Attitude.cpp
@@ -133,7 +133,7 @@ float Sub::get_surface_tracking_climb_rate(int16_t target_rate, float current_al
     float velocity_correction;
     float current_alt = inertial_nav.get_altitude();
 
-    uint32_t now = millis();
+    uint32_t now = AP_HAL::millis();
 
     // reset target altitude if this controller has just been engaged
     if (now - last_call_ms > RANGEFINDER_TIMEOUT_MS) {
diff --git a/ArduSub/GCS_Mavlink.cpp b/ArduSub/GCS_Mavlink.cpp
index 6e605edd0e..f0c6ec6578 100644
--- a/ArduSub/GCS_Mavlink.cpp
+++ b/ArduSub/GCS_Mavlink.cpp
@@ -1285,7 +1285,7 @@ void Sub::mavlink_delay_cb()
 
     DataFlash.EnableWrites(false);
 
-    uint32_t tnow = millis();
+    uint32_t tnow = AP_HAL::millis();
     if (tnow - last_1hz > 1000) {
         last_1hz = tnow;
         gcs_send_heartbeat();
diff --git a/ArduSub/Sub.h b/ArduSub/Sub.h
index 0761e89415..f55fe94e93 100644
--- a/ArduSub/Sub.h
+++ b/ArduSub/Sub.h
@@ -724,5 +724,4 @@ public:
 extern const AP_HAL::HAL& hal;
 extern Sub sub;
 
-using AP_HAL::millis;
 using AP_HAL::micros;
diff --git a/ArduSub/commands_logic.cpp b/ArduSub/commands_logic.cpp
index 1a4e0358fe..691fc6d3ca 100644
--- a/ArduSub/commands_logic.cpp
+++ b/ArduSub/commands_logic.cpp
@@ -519,7 +519,7 @@ void Sub::do_nav_guided_enable(const AP_Mission::Mission_Command& cmd)
 // do_nav_delay - Delay the next navigation command
 void Sub::do_nav_delay(const AP_Mission::Mission_Command& cmd)
 {
-    nav_delay_time_start = millis();
+    nav_delay_time_start = AP_HAL::millis();
 
     if (cmd.content.nav_delay.seconds > 0) {
         // relative delay
@@ -580,11 +580,11 @@ bool Sub::verify_nav_wp(const AP_Mission::Mission_Command& cmd)
 
     // start timer if necessary
     if (loiter_time == 0) {
-        loiter_time = millis();
+        loiter_time = AP_HAL::millis();
     }
 
     // check if timer has run out
-    if (((millis() - loiter_time) / 1000) >= loiter_time_max) {
+    if (((AP_HAL::millis() - loiter_time) / 1000) >= loiter_time_max) {
         gcs().send_text(MAV_SEVERITY_INFO, "Reached command #%i",cmd.index);
         return true;
     }
@@ -648,11 +648,11 @@ bool Sub::verify_loiter_time()
 
     // start our loiter timer
     if (loiter_time == 0) {
-        loiter_time = millis();
+        loiter_time = AP_HAL::millis();
     }
 
     // check if loiter timer has run out
-    return (((millis() - loiter_time) / 1000) >= loiter_time_max);
+    return (((AP_HAL::millis() - loiter_time) / 1000) >= loiter_time_max);
 }
 
 // verify_circle - check if we have circled the point enough
@@ -695,11 +695,11 @@ bool Sub::verify_spline_wp(const AP_Mission::Mission_Command& cmd)
 
     // start timer if necessary
     if (loiter_time == 0) {
-        loiter_time = millis();
+        loiter_time = AP_HAL::millis();
     }
 
     // check if timer has run out
-    if (((millis() - loiter_time) / 1000) >= loiter_time_max) {
+    if (((AP_HAL::millis() - loiter_time) / 1000) >= loiter_time_max) {
         gcs().send_text(MAV_SEVERITY_INFO, "Reached command #%i",cmd.index);
         return true;
     }
@@ -724,7 +724,7 @@ bool Sub::verify_nav_guided_enable(const AP_Mission::Mission_Command& cmd)
 // verify_nav_delay - check if we have waited long enough
 bool Sub::verify_nav_delay(const AP_Mission::Mission_Command& cmd)
 {
-    if (millis() - nav_delay_time_start > (uint32_t)MAX(nav_delay_time_max,0)) {
+    if (AP_HAL::millis() - nav_delay_time_start > (uint32_t)MAX(nav_delay_time_max, 0)) {
         nav_delay_time_max = 0;
         return true;
     }
@@ -737,7 +737,7 @@ bool Sub::verify_nav_delay(const AP_Mission::Mission_Command& cmd)
 
 void Sub::do_wait_delay(const AP_Mission::Mission_Command& cmd)
 {
-    condition_start = millis();
+    condition_start = AP_HAL::millis();
     condition_value = cmd.content.delay.seconds * 1000;     // convert seconds to milliseconds
 }
 
@@ -762,7 +762,7 @@ void Sub::do_yaw(const AP_Mission::Mission_Command& cmd)
 
 bool Sub::verify_wait_delay()
 {
-    if (millis() - condition_start > (uint32_t)MAX(condition_value,0)) {
+    if (AP_HAL::millis() - condition_start > (uint32_t)MAX(condition_value, 0)) {
         condition_value = 0;
         return true;
     }
diff --git a/ArduSub/control_guided.cpp b/ArduSub/control_guided.cpp
index 0edf56ea57..f2562424bd 100644
--- a/ArduSub/control_guided.cpp
+++ b/ArduSub/control_guided.cpp
@@ -125,7 +125,7 @@ void Sub::guided_angle_control_start()
     pos_control.set_desired_velocity_z(inertial_nav.get_velocity_z());
 
     // initialise targets
-    guided_angle_state.update_time_ms = millis();
+    guided_angle_state.update_time_ms = AP_HAL::millis();
     guided_angle_state.roll_cd = ahrs.roll_sensor;
     guided_angle_state.pitch_cd = ahrs.pitch_sensor;
     guided_angle_state.yaw_cd = ahrs.yaw_sensor;
@@ -203,7 +203,7 @@ void Sub::guided_set_velocity(const Vector3f& velocity)
         guided_vel_control_start();
     }
 
-    vel_update_time_ms = millis();
+    vel_update_time_ms = AP_HAL::millis();
 
     // set position controller velocity target
     pos_control.set_desired_velocity(velocity);
@@ -227,7 +227,7 @@ bool Sub::guided_set_destination_posvel(const Vector3f& destination, const Vecto
     }
 #endif
 
-    posvel_update_time_ms = millis();
+    posvel_update_time_ms = AP_HAL::millis();
     posvel_pos_target_cm = destination;
     posvel_vel_target_cms = velocity;
 
@@ -253,7 +253,7 @@ void Sub::guided_set_angle(const Quaternion &q, float climb_rate_cms)
     guided_angle_state.yaw_cd = wrap_180_cd(ToDeg(guided_angle_state.yaw_cd) * 100.0f);
 
     guided_angle_state.climb_rate_cms = climb_rate_cms;
-    guided_angle_state.update_time_ms = millis();
+    guided_angle_state.update_time_ms = AP_HAL::millis();
 }
 
 // guided_run - runs the guided controller
@@ -363,7 +363,7 @@ void Sub::guided_vel_control_run()
     motors.set_desired_spool_state(AP_Motors::DESIRED_THROTTLE_UNLIMITED);
 
     // set velocity to zero if no updates received for 3 seconds
-    uint32_t tnow = millis();
+    uint32_t tnow = AP_HAL::millis();
     if (tnow - vel_update_time_ms > GUIDED_POSVEL_TIMEOUT_MS && !pos_control.get_desired_velocity().is_zero()) {
         pos_control.set_desired_velocity(Vector3f(0,0,0));
     }
@@ -419,7 +419,7 @@ void Sub::guided_posvel_control_run()
     motors.set_desired_spool_state(AP_Motors::DESIRED_THROTTLE_UNLIMITED);
 
     // set velocity to zero if no updates received for 3 seconds
-    uint32_t tnow = millis();
+    uint32_t tnow = AP_HAL::millis();
     if (tnow - posvel_update_time_ms > GUIDED_POSVEL_TIMEOUT_MS && !posvel_vel_target_cms.is_zero()) {
         posvel_vel_target_cms.zero();
     }
@@ -493,7 +493,7 @@ void Sub::guided_angle_control_run()
     float climb_rate_cms = constrain_float(guided_angle_state.climb_rate_cms, -fabsf(wp_nav.get_speed_down()), wp_nav.get_speed_up());
 
     // check for timeout - set lean angles and climb rate to zero if no updates received for 3 seconds
-    uint32_t tnow = millis();
+    uint32_t tnow = AP_HAL::millis();
     if (tnow - guided_angle_state.update_time_ms > GUIDED_ATTITUDE_TIMEOUT_MS) {
         roll_in = 0.0f;
         pitch_in = 0.0f;
@@ -547,7 +547,7 @@ void Sub::guided_limit_init_time_and_pos()
 bool Sub::guided_limit_check()
 {
     // check if we have passed the timeout
-    if ((guided_limit.timeout_ms > 0) && (millis() - guided_limit.start_time >= guided_limit.timeout_ms)) {
+    if ((guided_limit.timeout_ms > 0) && (AP_HAL::millis() - guided_limit.start_time >= guided_limit.timeout_ms)) {
         return true;
     }
 
diff --git a/ArduSub/failsafe.cpp b/ArduSub/failsafe.cpp
index 20b63a4739..79acf48873 100644
--- a/ArduSub/failsafe.cpp
+++ b/ArduSub/failsafe.cpp
@@ -441,7 +441,7 @@ void Sub::failsafe_terrain_check()
 // set terrain data status (found or not found)
 void Sub::failsafe_terrain_set_status(bool data_ok)
 {
-    uint32_t now = millis();
+    uint32_t now = AP_HAL::millis();
 
     // record time of first and latest failures (i.e. duration of failures)
     if (!data_ok) {