diff --git a/libraries/SITL/SIM_RF_LightWareSerial.cpp b/libraries/SITL/SIM_RF_LightWareSerial.cpp
index ef6299fcd8..bf44e40806 100644
--- a/libraries/SITL/SIM_RF_LightWareSerial.cpp
+++ b/libraries/SITL/SIM_RF_LightWareSerial.cpp
@@ -50,5 +50,10 @@ void RF_LightWareSerial::update(float range)
 
 uint32_t RF_LightWareSerial::packet_for_alt(uint16_t alt_cm, uint8_t *buffer, uint8_t buflen)
 {
+    if (alt_cm > 10000) {
+        // out-of-range-high
+        alt_cm = 13000;  // from datasheet
+    }
+
     return snprintf((char*)buffer, buflen, "%0.2f\r", alt_cm / 100.0f); // note tragic lack of snprintf return checking
 }