diff --git a/libraries/AC_AutoTune/AC_AutoTune_Multi.cpp b/libraries/AC_AutoTune/AC_AutoTune_Multi.cpp
index 5e7aa6c5d9..2f86b6d829 100644
--- a/libraries/AC_AutoTune/AC_AutoTune_Multi.cpp
+++ b/libraries/AC_AutoTune/AC_AutoTune_Multi.cpp
@@ -644,7 +644,7 @@ void AC_AutoTune_Multi::twitching_test_angle(float angle, float rate, float angl
 }
 
 // twitching_measure_acceleration - measure rate of change of measurement
-void AC_AutoTune_Multi::twitching_measure_acceleration(float &accel_average, float rate, float rate_max) const
+void AC_AutoTune_Multi::twitching_measure_acceleration(float &accel_average, float rate, float &rate_max) const
 {
     if (rate_max < rate) {
         rate_max = rate;
diff --git a/libraries/AC_AutoTune/AC_AutoTune_Multi.h b/libraries/AC_AutoTune/AC_AutoTune_Multi.h
index e89dd4c589..6987c1c252 100644
--- a/libraries/AC_AutoTune/AC_AutoTune_Multi.h
+++ b/libraries/AC_AutoTune/AC_AutoTune_Multi.h
@@ -156,7 +156,7 @@ private:
     void twitching_test_angle(float angle, float rate, float angle_target, float &meas_angle_min, float &meas_angle_max, float &meas_rate_min, float &meas_rate_max);
 
     // measure acceleration during twitch test
-    void twitching_measure_acceleration(float &accel_average, float rate, float rate_max) const;
+    void twitching_measure_acceleration(float &accel_average, float rate, float &rate_max) const;
 
     // updating_rate_d_up - increase D and adjust P to optimize the D term for a little bounce back
     // optimize D term while keeping the maximum just below the target by adjusting P