diff --git a/ArduPlane/sensors.cpp b/ArduPlane/sensors.cpp
index 0271557c06..1d3c65f27d 100644
--- a/ArduPlane/sensors.cpp
+++ b/ArduPlane/sensors.cpp
@@ -46,8 +46,9 @@ void Plane::read_rangefinder(void)
 
     rangefinder.update();
 
-    if (should_log(MASK_LOG_SONAR))
+    if ((rangefinder.num_sensors() > 0) && should_log(MASK_LOG_SONAR)) {
         Log_Write_Sonar();
+    }
 
     rangefinder_height_update();
 }