diff --git a/libraries/AP_ADSB/AP_ADSB.cpp b/libraries/AP_ADSB/AP_ADSB.cpp
index dd8ecd702b..b2d6f466c8 100644
--- a/libraries/AP_ADSB/AP_ADSB.cpp
+++ b/libraries/AP_ADSB/AP_ADSB.cpp
@@ -175,7 +175,7 @@ void AP_ADSB::perform_threat_detection(void)
 Location AP_ADSB::get_location(const adsb_vehicle_t &vehicle) const
 {
     Location loc {};
-    loc.alt = vehicle.info.altitude * 100;
+    loc.alt = vehicle.info.altitude * 10; // convert mm to cm.
     loc.lat = vehicle.info.lat;
     loc.lng = vehicle.info.lon;
     loc.flags.relative_alt = false;
diff --git a/libraries/AP_ADSB/AP_ADSB.h b/libraries/AP_ADSB/AP_ADSB.h
index e4cfc1d4e5..485f8f8813 100644
--- a/libraries/AP_ADSB/AP_ADSB.h
+++ b/libraries/AP_ADSB/AP_ADSB.h
@@ -46,7 +46,7 @@ public:
     };
 
     struct adsb_vehicle_t {
-        mavlink_adsb_vehicle_t info; // the whole mavlink struct with all the juicy details. sizeof() == 42
+        mavlink_adsb_vehicle_t info; // the whole mavlink struct with all the juicy details. sizeof() == 38
         uint32_t last_update_ms; // last time this was refreshed, allows timeouts
         ADSB_THREAT_LEVEL threat_level;   // basic threat level
     };