diff --git a/libraries/AC_WPNav/AC_WPNav.cpp b/libraries/AC_WPNav/AC_WPNav.cpp
index 601f331753..e27705c25d 100644
--- a/libraries/AC_WPNav/AC_WPNav.cpp
+++ b/libraries/AC_WPNav/AC_WPNav.cpp
@@ -113,7 +113,7 @@ AC_WPNav::AC_WPNav(const AP_InertialNav& inav, const AP_AHRS_View& ahrs, AC_PosC
     _flags.fast_waypoint = false;
 
     // initialise old WPNAV_SPEED value
-    _last_wp_speed_cms = _wp_speed_down_cms;
+    _last_wp_speed_cms = get_default_speed_down();
 }
 
 // get expected source of terrain data if alt-above-terrain command is executed (used by Copter's ModeRTL)
@@ -167,8 +167,8 @@ void AC_WPNav::wp_and_spline_init(float speed_cms)
     // initialise position controller speed and acceleration
     _pos_control.set_max_speed_accel_xy(_wp_desired_speed_xy_cms, _wp_accel_cmss);
     _pos_control.set_correction_speed_accel_xy(_wp_desired_speed_xy_cms, _wp_accel_cmss);
-    _pos_control.set_max_speed_accel_z(-_wp_speed_down_cms, _wp_speed_up_cms, _wp_accel_z_cmss);
-    _pos_control.set_correction_speed_accel_z(-_wp_speed_down_cms, _wp_speed_up_cms, _wp_accel_z_cmss);
+    _pos_control.set_max_speed_accel_z(-get_default_speed_down(), _wp_speed_up_cms, _wp_accel_z_cmss);
+    _pos_control.set_correction_speed_accel_z(-get_default_speed_down(), _wp_speed_up_cms, _wp_accel_z_cmss);
 
     // calculate scurve jerk and jerk time
     if (!is_positive(_wp_jerk)) {
diff --git a/libraries/AC_WPNav/AC_WPNav.h b/libraries/AC_WPNav/AC_WPNav.h
index 27542625dd..a4585d3926 100644
--- a/libraries/AC_WPNav/AC_WPNav.h
+++ b/libraries/AC_WPNav/AC_WPNav.h
@@ -71,7 +71,7 @@ public:
     float get_default_speed_up() const { return _wp_speed_up_cms; }
 
     /// get default target descent rate in cm/s during missions.  Note: always positive
-    float get_default_speed_down() const { return _wp_speed_down_cms; }
+    float get_default_speed_down() const { return fabsf(_wp_speed_down_cms); }
 
     /// get_speed_z - returns target descent speed in cm/s during missions.  Note: always positive
     float get_accel_z() const { return _wp_accel_z_cmss; }