diff --git a/libraries/AC_AttitudeControl/AC_PosControl.cpp b/libraries/AC_AttitudeControl/AC_PosControl.cpp
index 13bf6ad28f..9b3c422e75 100644
--- a/libraries/AC_AttitudeControl/AC_PosControl.cpp
+++ b/libraries/AC_AttitudeControl/AC_PosControl.cpp
@@ -46,6 +46,7 @@ AC_PosControl::AC_PosControl(const AP_AHRS& ahrs, const AP_InertialNav& inav,
     _speed_up_cms(POSCONTROL_SPEED_UP),
     _speed_cms(POSCONTROL_SPEED),
     _accel_z_cms(POSCONTROL_ACCEL_Z),
+    _accel_last_z_cms(0.0f),
     _accel_cms(POSCONTROL_ACCEL_XY),
     _leash(POSCONTROL_LEASH_LENGTH_MIN),
     _leash_down_z(POSCONTROL_LEASH_LENGTH_MIN),