diff --git a/libraries/AC_AutoTune/AC_AutoTune_Multi.cpp b/libraries/AC_AutoTune/AC_AutoTune_Multi.cpp
index 3c27209813..606480f4ed 100644
--- a/libraries/AC_AutoTune/AC_AutoTune_Multi.cpp
+++ b/libraries/AC_AutoTune/AC_AutoTune_Multi.cpp
@@ -130,13 +130,15 @@ void AC_AutoTune_Multi::do_gcs_announcements()
     case RP_UP:
         gcs().send_text(MAV_SEVERITY_INFO, "AutoTune: p=%f d=%f", (double)tune_rp, (double)tune_rd);
         break;
-    case RFF_UP:
-        break;
     case SP_DOWN:
     case SP_UP:
         gcs().send_text(MAV_SEVERITY_INFO, "AutoTune: p=%f accel=%f", (double)tune_sp, (double)tune_accel);
         break;
+    case RFF_UP:
     case MAX_GAINS:
+        // this should never happen
+        INTERNAL_ERROR(AP_InternalError::error_t::flow_of_control);
+        break;
     case TUNE_COMPLETE:
         break;
     }
@@ -728,6 +730,9 @@ void AC_AutoTune_Multi::set_gains_post_tune(AxisType test_axis)
         break;
     case RFF_UP:
     case MAX_GAINS:
+        // this should never happen
+        INTERNAL_ERROR(AP_InternalError::error_t::flow_of_control);
+        break;
     case TUNE_COMPLETE:
         break;
     }
@@ -1172,6 +1177,11 @@ void AC_AutoTune_Multi::twitch_test_run(AxisType test_axis, const float dir_sign
         twitching_test_angle(lean_angle, rotation_rate, target_angle*(1+0.5f*aggressiveness), test_angle_min, test_angle_max, test_rate_min, test_rate_max);
         twitching_measure_acceleration(test_accel_max, rotation_rate - dir_sign * start_rate, rate_max);
         break;
+    case RFF_UP:
+    case MAX_GAINS:
+        // this should never happen
+        INTERNAL_ERROR(AP_InternalError::error_t::flow_of_control);
+        break;
     default:
         break;
     }
diff --git a/libraries/AC_AutoTune/AC_AutoTune_Multi.h b/libraries/AC_AutoTune/AC_AutoTune_Multi.h
index 30c3f5ef14..b7e826b80e 100644
--- a/libraries/AC_AutoTune/AC_AutoTune_Multi.h
+++ b/libraries/AC_AutoTune/AC_AutoTune_Multi.h
@@ -54,7 +54,10 @@ protected:
     void load_test_gains() override;
 
     // reset the test vaariables for heli
-    void reset_vehicle_test_variables() override {};
+    void reset_vehicle_test_variables() override {
+        // this should never happen
+        INTERNAL_ERROR(AP_InternalError::error_t::flow_of_control);
+    }
 
     void test_init() override;
     void test_run(AxisType test_axis, const float dir_sign) override;
@@ -70,7 +73,10 @@ protected:
     void updating_rate_d_down_all(AxisType test_axis) override;
 
     // update gains for the rate ff up tune type
-    void updating_rate_ff_up_all(AxisType test_axis) override {};
+    void updating_rate_ff_up_all(AxisType test_axis) override {
+        // this should never happen
+        INTERNAL_ERROR(AP_InternalError::error_t::flow_of_control);
+    }
 
     // update gains for the angle P up tune type
     void updating_angle_p_up_all(AxisType test_axis) override;
@@ -79,7 +85,10 @@ protected:
     void updating_angle_p_down_all(AxisType test_axis) override;
 
     // update gains for the max gain tune type
-    void updating_max_gains_all(AxisType test_axis) override {};
+    void updating_max_gains_all(AxisType test_axis) override {
+        // this should never happen
+        INTERNAL_ERROR(AP_InternalError::error_t::flow_of_control);
+    }
 
     // set gains post tune for the tune type
     void set_gains_post_tune(AxisType test_axis) override;
@@ -89,7 +98,10 @@ protected:
 
     void Log_AutoTune() override;
     void Log_AutoTuneDetails() override;
-    void Log_AutoTuneSweep() override {};
+    void Log_AutoTuneSweep() override {
+        // this should never happen
+        INTERNAL_ERROR(AP_InternalError::error_t::flow_of_control);
+    }
     void Log_Write_AutoTune(uint8_t axis, uint8_t tune_step, float meas_target, float meas_min, float meas_max, float new_gain_rp, float new_gain_rd, float new_gain_sp, float new_ddt);
     void Log_Write_AutoTuneDetails(float angle_cd, float rate_cds);