diff --git a/ArduSub/GCS_Mavlink.cpp b/ArduSub/GCS_Mavlink.cpp
index 149507e1be..78a3e288b9 100644
--- a/ArduSub/GCS_Mavlink.cpp
+++ b/ArduSub/GCS_Mavlink.cpp
@@ -374,7 +374,9 @@ static const ap_message STREAM_RC_CHANNELS_msgs[] = {
 };
 static const ap_message STREAM_EXTRA1_msgs[] = {
     MSG_ATTITUDE,
+#if AP_SIM_ENABLED
     MSG_SIMSTATE,
+#endif
     MSG_AHRS2,
     MSG_PID_TUNING
 };