diff --git a/libraries/AP_GPS/AP_GPS_MAV.cpp b/libraries/AP_GPS/AP_GPS_MAV.cpp
index c7078b4f7c..92fb607948 100644
--- a/libraries/AP_GPS/AP_GPS_MAV.cpp
+++ b/libraries/AP_GPS/AP_GPS_MAV.cpp
@@ -132,12 +132,15 @@ void AP_GPS_MAV::handle_msg(const mavlink_message_t *msg)
             }
             Vector3f vel(packet.vn/100.0f, packet.ve/100.0f, packet.vd/100.0f);
             state.velocity = vel;
+            if (packet.vd != 0) {
+                state.have_vertical_velocity = true;
+            }
             if (packet.cog < 36000) {
                 state.ground_course = packet.cog / 100.0f;
             }
             state.have_speed_accuracy = false;
-            state.have_horizontal_accuracy = 0;
-            state.have_vertical_accuracy = 0;
+            state.have_horizontal_accuracy = false;
+            state.have_vertical_accuracy = false;
             if (packet.satellites_visible < 255) {
                 state.num_sats = packet.satellites_visible;
             }