diff --git a/libraries/SITL/SIM_Ship.cpp b/libraries/SITL/SIM_Ship.cpp
index 0af352ecea..b45699eab8 100644
--- a/libraries/SITL/SIM_Ship.cpp
+++ b/libraries/SITL/SIM_Ship.cpp
@@ -185,8 +185,13 @@ void ShipSim::send_report(void)
         last_heartbeat_ms = now;
 
         const mavlink_heartbeat_t heartbeat{
+        custom_mode: 0,
         type : MAV_TYPE_SURFACE_BOAT,
-        autopilot : MAV_AUTOPILOT_INVALID};
+        autopilot : MAV_AUTOPILOT_INVALID,
+        base_mode: 0,
+        system_status: 0,
+        mavlink_version: 0,
+        };
 
         mavlink_message_t msg;
         mavlink_msg_heartbeat_encode_status(
diff --git a/libraries/SITL/SIM_Vicon.cpp b/libraries/SITL/SIM_Vicon.cpp
index df55518ab0..ea86270f69 100644
--- a/libraries/SITL/SIM_Vicon.cpp
+++ b/libraries/SITL/SIM_Vicon.cpp
@@ -50,8 +50,12 @@ void Vicon::maybe_send_heartbeat()
     last_heartbeat_ms = now;
 
     const mavlink_heartbeat_t heartbeat{
-    type : MAV_TYPE_GCS,
-    autopilot : MAV_AUTOPILOT_INVALID,
+        custom_mode: 0,
+        type : MAV_TYPE_GCS,
+        autopilot : MAV_AUTOPILOT_INVALID,
+        base_mode: 0,
+        system_status: 0,
+        mavlink_version: 0,
     };
 
     mavlink_msg_heartbeat_encode_status(