diff --git a/libraries/AP_RangeFinder/AP_RangeFinder.cpp b/libraries/AP_RangeFinder/AP_RangeFinder.cpp
index 7adc758f05..c487eb2eba 100644
--- a/libraries/AP_RangeFinder/AP_RangeFinder.cpp
+++ b/libraries/AP_RangeFinder/AP_RangeFinder.cpp
@@ -745,7 +745,7 @@ MAV_DISTANCE_SENSOR RangeFinder::get_mav_distance_sensor_type_orient(enum Rotati
 }
 
 // Write an RFND (rangefinder) packet
-void RangeFinder::Log_RFND()
+void RangeFinder::Log_RFND() const
 {
     if (_log_rfnd_bit == uint32_t(-1)) {
         return;
diff --git a/libraries/AP_RangeFinder/AP_RangeFinder.h b/libraries/AP_RangeFinder/AP_RangeFinder.h
index 4f8854f869..8f805e7786 100644
--- a/libraries/AP_RangeFinder/AP_RangeFinder.h
+++ b/libraries/AP_RangeFinder/AP_RangeFinder.h
@@ -212,7 +212,7 @@ private:
     bool _add_backend(AP_RangeFinder_Backend *driver, uint8_t instance);
 
     uint32_t _log_rfnd_bit = -1;
-    void Log_RFND();
+    void Log_RFND() const;
 };
 
 namespace AP {
diff --git a/libraries/AP_RangeFinder/AP_RangeFinder_BLPing.cpp b/libraries/AP_RangeFinder/AP_RangeFinder_BLPing.cpp
index 6d3b6e690f..ea3e28593b 100644
--- a/libraries/AP_RangeFinder/AP_RangeFinder_BLPing.cpp
+++ b/libraries/AP_RangeFinder/AP_RangeFinder_BLPing.cpp
@@ -55,7 +55,7 @@ bool AP_RangeFinder_BLPing::get_reading(uint16_t &reading_cm)
     struct {
         float sum_cm = 0;
         uint16_t count = 0;
-        float mean() { return sum_cm / count; };
+        float mean() const { return sum_cm / count; };
     } averageStruct;
 
     // read any available lines from the lidar
diff --git a/libraries/AP_RangeFinder/AP_RangeFinder_VL53L1X.cpp b/libraries/AP_RangeFinder/AP_RangeFinder_VL53L1X.cpp
index 3ad272dcd8..17f43c0554 100644
--- a/libraries/AP_RangeFinder/AP_RangeFinder_VL53L1X.cpp
+++ b/libraries/AP_RangeFinder/AP_RangeFinder_VL53L1X.cpp
@@ -402,7 +402,7 @@ uint32_t AP_RangeFinder_VL53L1X::timeoutMicrosecondsToMclks(uint32_t timeout_us,
 // Calculate macro period in microseconds (12.12 format) with given VCSEL period
 // assumes fast_osc_frequency has been read and stored
 // based on VL53L1_calc_macro_period_us()
-uint32_t AP_RangeFinder_VL53L1X::calcMacroPeriod(uint8_t vcsel_period)
+uint32_t AP_RangeFinder_VL53L1X::calcMacroPeriod(uint8_t vcsel_period) const
 {
     // from VL53L1_calc_pll_period_us()
     // fast osc frequency in 4.12 format; PLL period in 0.24 format
diff --git a/libraries/AP_RangeFinder/AP_RangeFinder_VL53L1X.h b/libraries/AP_RangeFinder/AP_RangeFinder_VL53L1X.h
index 742d0b053f..5cd6efe58e 100644
--- a/libraries/AP_RangeFinder/AP_RangeFinder_VL53L1X.h
+++ b/libraries/AP_RangeFinder/AP_RangeFinder_VL53L1X.h
@@ -1290,6 +1290,6 @@ private:
     uint16_t encodeTimeout(uint32_t timeout_mclks);
     uint32_t timeoutMclksToMicroseconds(uint32_t timeout_mclks, uint32_t macro_period_us);
     uint32_t timeoutMicrosecondsToMclks(uint32_t timeout_us, uint32_t macro_period_us);
-    uint32_t calcMacroPeriod(uint8_t vcsel_period);
+    uint32_t calcMacroPeriod(uint8_t vcsel_period) const;
     bool setupManualCalibration(void);
 };