diff --git a/libraries/AP_DAL/AP_DAL_RangeFinder.cpp b/libraries/AP_DAL/AP_DAL_RangeFinder.cpp
index 23e5ed9180..0d83c518c9 100644
--- a/libraries/AP_DAL/AP_DAL_RangeFinder.cpp
+++ b/libraries/AP_DAL/AP_DAL_RangeFinder.cpp
@@ -116,7 +116,10 @@ bool AP_DAL_RangeFinder::has_orientation(enum Rotation orientation) const
 AP_DAL_RangeFinder_Backend *AP_DAL_RangeFinder::get_backend(uint8_t id) const
 {
    if (id >= RANGEFINDER_MAX_INSTANCES) {
-        INTERNAL_ERROR(AP_InternalError::error_t::flow_of_control);
+       INTERNAL_ERROR(AP_InternalError::error_t::flow_of_control);
+       return nullptr;
+   }
+   if (id >= _RRNH.num_sensors) {
         return nullptr;
     }