diff --git a/libraries/AP_NavEKF2/AP_NavEKF2_PosVelFusion.cpp b/libraries/AP_NavEKF2/AP_NavEKF2_PosVelFusion.cpp
index bb36841c45..5d3de168f2 100644
--- a/libraries/AP_NavEKF2/AP_NavEKF2_PosVelFusion.cpp
+++ b/libraries/AP_NavEKF2/AP_NavEKF2_PosVelFusion.cpp
@@ -278,7 +278,7 @@ void NavEKF2_core::CorrectGPSForAntennaOffset(gps_elements &gps_data) const
 }
 
 // correct external navigation earth-frame position using sensor body-frame offset
-void NavEKF2_core::CorrectExtNavForSensorOffset(Vector3f &ext_position)
+void NavEKF2_core::CorrectExtNavForSensorOffset(Vector3f &ext_position) const
 {
 #if HAL_VISUALODOM_ENABLED
     AP_VisualOdom *visual_odom = AP::visualodom();
diff --git a/libraries/AP_NavEKF2/AP_NavEKF2_core.h b/libraries/AP_NavEKF2/AP_NavEKF2_core.h
index a2a3de7649..bf60f2065e 100644
--- a/libraries/AP_NavEKF2/AP_NavEKF2_core.h
+++ b/libraries/AP_NavEKF2/AP_NavEKF2_core.h
@@ -780,7 +780,7 @@ private:
     void CorrectGPSForAntennaOffset(gps_elements &gps_data) const;
 
     // correct external navigation earth-frame position using sensor body-frame offset
-    void CorrectExtNavForSensorOffset(Vector3f &ext_position);
+    void CorrectExtNavForSensorOffset(Vector3f &ext_position) const;
 
     // Length of FIFO buffers used for non-IMU sensor data.
     // Must be larger than the time period defined by IMU_BUFFER_LENGTH