diff --git a/ArduCopter/Copter.h b/ArduCopter/Copter.h
index 86a1cf09fa..1d6f207764 100644
--- a/ArduCopter/Copter.h
+++ b/ArduCopter/Copter.h
@@ -588,6 +588,15 @@ private:
     static const AP_Param::Info var_info[];
     static const struct LogStructure log_structure[];
 
+    // enum for ESC CALIBRATION
+    enum ESCCalibrationModes : uint8_t {
+        ESCCAL_NONE = 0,
+        ESCCAL_PASSTHROUGH_IF_THROTTLE_HIGH = 1,
+        ESCCAL_PASSTHROUGH_ALWAYS = 2,
+        ESCCAL_AUTO = 3,
+        ESCCAL_DISABLED = 9,
+    };
+
     enum Failsafe_Action {
         Failsafe_Action_None           = 0,
         Failsafe_Action_Land           = 1,
diff --git a/ArduCopter/GCS_Mavlink.cpp b/ArduCopter/GCS_Mavlink.cpp
index 8866fd63a4..3cb091e112 100644
--- a/ArduCopter/GCS_Mavlink.cpp
+++ b/ArduCopter/GCS_Mavlink.cpp
@@ -558,6 +558,18 @@ MAV_RESULT GCS_MAVLINK_Copter::handle_command_do_set_roi(const Location &roi_loc
     return MAV_RESULT_ACCEPTED;
 }
 
+MAV_RESULT GCS_MAVLINK_Copter::handle_preflight_reboot(const mavlink_command_long_t &packet)
+{
+    // reject reboot if user has also specified they want the "Auto" ESC calibration on next reboot
+    if (copter.g.esc_calibrate == (uint8_t)Copter::ESCCalibrationModes::ESCCAL_AUTO) {
+        send_text(MAV_SEVERITY_CRITICAL, "Reboot rejected, ESC cal on reboot");
+        return MAV_RESULT_FAILED;
+    }
+
+    // call parent
+    return GCS_MAVLINK::handle_preflight_reboot(packet);
+}
+
 bool GCS_MAVLINK_Copter::set_home_to_current_location(bool lock) {
     return copter.set_home_to_current_location(lock);
 }
diff --git a/ArduCopter/GCS_Mavlink.h b/ArduCopter/GCS_Mavlink.h
index 7b60a03947..abb4202987 100644
--- a/ArduCopter/GCS_Mavlink.h
+++ b/ArduCopter/GCS_Mavlink.h
@@ -29,7 +29,7 @@ protected:
     void send_position_target_local_ned() override;
 
     MAV_RESULT handle_command_do_set_roi(const Location &roi_loc) override;
-
+    MAV_RESULT handle_preflight_reboot(const mavlink_command_long_t &packet) override;
     MAV_RESULT handle_command_mount(const mavlink_command_long_t &packet) override;
     MAV_RESULT handle_command_int_packet(const mavlink_command_int_t &packet) override;
     MAV_RESULT handle_command_long_packet(const mavlink_command_long_t &packet) override;
diff --git a/ArduCopter/esc_calibration.cpp b/ArduCopter/esc_calibration.cpp
index f39dd9adbf..152388d1ed 100644
--- a/ArduCopter/esc_calibration.cpp
+++ b/ArduCopter/esc_calibration.cpp
@@ -6,15 +6,6 @@
 
 #define ESC_CALIBRATION_HIGH_THROTTLE   950
 
-// enum for ESC CALIBRATION
-enum ESCCalibrationModes {
-    ESCCAL_NONE = 0,
-    ESCCAL_PASSTHROUGH_IF_THROTTLE_HIGH = 1,
-    ESCCAL_PASSTHROUGH_ALWAYS = 2,
-    ESCCAL_AUTO = 3,
-    ESCCAL_DISABLED = 9,
-};
-
 // check if we should enter esc calibration mode
 void Copter::esc_calibration_startup_check()
 {
@@ -34,19 +25,19 @@ void Copter::esc_calibration_startup_check()
     // exit immediately if pre-arm rc checks fail
     if (!arming.rc_calibration_checks(true)) {
         // clear esc flag for next time
-        if ((g.esc_calibrate != ESCCAL_NONE) && (g.esc_calibrate != ESCCAL_DISABLED)) {
-            g.esc_calibrate.set_and_save(ESCCAL_NONE);
+        if ((g.esc_calibrate != ESCCalibrationModes::ESCCAL_NONE) && (g.esc_calibrate != ESCCalibrationModes::ESCCAL_DISABLED)) {
+            g.esc_calibrate.set_and_save(ESCCalibrationModes::ESCCAL_NONE);
         }
         return;
     }
 
     // check ESC parameter
     switch (g.esc_calibrate) {
-        case ESCCAL_NONE:
+        case ESCCalibrationModes::ESCCAL_NONE:
             // check if throttle is high
             if (channel_throttle->get_control_in() >= ESC_CALIBRATION_HIGH_THROTTLE) {
                 // we will enter esc_calibrate mode on next reboot
-                g.esc_calibrate.set_and_save(ESCCAL_PASSTHROUGH_IF_THROTTLE_HIGH);
+                g.esc_calibrate.set_and_save(ESCCalibrationModes::ESCCAL_PASSTHROUGH_IF_THROTTLE_HIGH);
                 // send message to gcs
                 gcs().send_text(MAV_SEVERITY_CRITICAL,"ESC calibration: Restart board");
                 // turn on esc calibration notification
@@ -55,30 +46,30 @@ void Copter::esc_calibration_startup_check()
                 while(1) { hal.scheduler->delay(5); }
             }
             break;
-        case ESCCAL_PASSTHROUGH_IF_THROTTLE_HIGH:
+        case ESCCalibrationModes::ESCCAL_PASSTHROUGH_IF_THROTTLE_HIGH:
             // check if throttle is high
             if (channel_throttle->get_control_in() >= ESC_CALIBRATION_HIGH_THROTTLE) {
                 // pass through pilot throttle to escs
                 esc_calibration_passthrough();
             }
             break;
-        case ESCCAL_PASSTHROUGH_ALWAYS:
+        case ESCCalibrationModes::ESCCAL_PASSTHROUGH_ALWAYS:
             // pass through pilot throttle to escs
             esc_calibration_passthrough();
             break;
-        case ESCCAL_AUTO:
+        case ESCCalibrationModes::ESCCAL_AUTO:
             // perform automatic ESC calibration
             esc_calibration_auto();
             break;
-        case ESCCAL_DISABLED:
+        case ESCCalibrationModes::ESCCAL_DISABLED:
         default:
             // do nothing
             break;
     }
 
     // clear esc flag for next time
-    if (g.esc_calibrate != ESCCAL_DISABLED) {
-        g.esc_calibrate.set_and_save(ESCCAL_NONE);
+    if (g.esc_calibrate != ESCCalibrationModes::ESCCAL_DISABLED) {
+        g.esc_calibrate.set_and_save(ESCCalibrationModes::ESCCAL_NONE);
     }
 #endif  // FRAME_CONFIG != HELI_FRAME
 }
@@ -189,4 +180,4 @@ void Copter::esc_calibration_setup()
     motors->armed(true);
     SRV_Channels::enable_by_mask(motors->get_motor_mask());
     hal.util->set_soft_armed(true);
-}
\ No newline at end of file
+}