diff --git a/ArduCopter/inertia.pde b/ArduCopter/inertia.pde
index 706d91dee1..49ebd4122f 100644
--- a/ArduCopter/inertia.pde
+++ b/ArduCopter/inertia.pde
@@ -10,6 +10,11 @@ static void read_inertia()
 // read_inertial_altitude - pull altitude and climb rate from inertial nav library
 static void read_inertial_altitude()
 {
+    // exit immediately if we do not have an altitude estimate or home is not set
+    if (!inertial_nav.get_filter_status().flags.vert_pos || (ap.home_state == HOME_UNSET)) {
+        return;
+    }
+
     // with inertial nav we can update the altitude and climb rate at 50hz
     current_loc.alt = pv_alt_above_home(inertial_nav.get_altitude());
     current_loc.flags.relative_alt = true;