diff --git a/libraries/AP_RangeFinder/AP_RangeFinder_Backend.h b/libraries/AP_RangeFinder/AP_RangeFinder_Backend.h
index 97a265fdec..2567f1a7b8 100644
--- a/libraries/AP_RangeFinder/AP_RangeFinder_Backend.h
+++ b/libraries/AP_RangeFinder/AP_RangeFinder_Backend.h
@@ -61,7 +61,7 @@ public:
     uint32_t last_reading_ms() const { return state.last_reading_ms; }
 
     // get temperature reading in C.  returns true on success and populates temp argument
-    virtual bool get_temp(float &temp) { return false; }
+    virtual bool get_temp(float &temp) const { return false; }
 
 protected:
 
diff --git a/libraries/AP_RangeFinder/AP_RangeFinder_NMEA.cpp b/libraries/AP_RangeFinder/AP_RangeFinder_NMEA.cpp
index 266f63c19e..e8c1caa604 100644
--- a/libraries/AP_RangeFinder/AP_RangeFinder_NMEA.cpp
+++ b/libraries/AP_RangeFinder/AP_RangeFinder_NMEA.cpp
@@ -50,7 +50,7 @@ bool AP_RangeFinder_NMEA::get_reading(uint16_t &reading_cm)
 }
 
 // get temperature reading
-bool AP_RangeFinder_NMEA::get_temp(float &temp)
+bool AP_RangeFinder_NMEA::get_temp(float &temp) const
 {
     uint32_t now_ms = AP_HAL::millis();
     if ((_temp_readtime_ms == 0) || ((now_ms - _temp_readtime_ms) > read_timeout_ms())) {
diff --git a/libraries/AP_RangeFinder/AP_RangeFinder_NMEA.h b/libraries/AP_RangeFinder/AP_RangeFinder_NMEA.h
index 52437c82ed..042a79a9ad 100644
--- a/libraries/AP_RangeFinder/AP_RangeFinder_NMEA.h
+++ b/libraries/AP_RangeFinder/AP_RangeFinder_NMEA.h
@@ -45,7 +45,7 @@ private:
     bool get_reading(uint16_t &reading_cm) override;
 
     // get temperature reading in C.  returns true on success and populates temp argument
-    bool get_temp(float &temp) override;
+    bool get_temp(float &temp) const override;
 
     uint16_t read_timeout_ms() const override { return 3000; }