diff --git a/libraries/SITL/SITL.cpp b/libraries/SITL/SITL.cpp
index a9b2a8ad92..7bb04953ad 100644
--- a/libraries/SITL/SITL.cpp
+++ b/libraries/SITL/SITL.cpp
@@ -65,6 +65,7 @@ const AP_Param::GroupInfo SITL::var_info[] PROGMEM = {
     AP_GROUPINFO("TERRAIN",       34, SITL,  terrain_enable, 1),
     AP_GROUPINFO("FLOW_RATE",     35, SITL,  flow_rate, 10),
     AP_GROUPINFO("FLOW_DELAY",    36, SITL,  flow_delay, 0),
+    AP_GROUPINFO("GPS_DRIFTALT",  37, SITL,  gps_drift_alt, 0),
     AP_GROUPEND
 };
 
diff --git a/libraries/SITL/SITL.h b/libraries/SITL/SITL.h
index da99268158..411d1721bb 100644
--- a/libraries/SITL/SITL.h
+++ b/libraries/SITL/SITL.h
@@ -90,6 +90,7 @@ public:
     AP_Float wind_speed;
     AP_Float wind_direction;
     AP_Float wind_turbulance;
+    AP_Float gps_drift_alt;
     
 	void simstate_send(mavlink_channel_t chan);