diff --git a/libraries/GCS_MAVLink/GCS.h b/libraries/GCS_MAVLink/GCS.h
index c26bc1ad8a..c53aebb9d0 100644
--- a/libraries/GCS_MAVLink/GCS.h
+++ b/libraries/GCS_MAVLink/GCS.h
@@ -354,11 +354,12 @@ protected:
     virtual MAV_RESULT _handle_command_preflight_calibration(const mavlink_command_long_t &packet);
     virtual MAV_RESULT _handle_command_preflight_calibration_baro();
 
+    void handle_command_long(mavlink_message_t* msg);
     MAV_RESULT handle_command_mag_cal(const mavlink_command_long_t &packet);
-    MAV_RESULT handle_command_long_message(mavlink_command_long_t &packet);
+    virtual MAV_RESULT handle_command_long_packet(const mavlink_command_long_t &packet);
     MAV_RESULT handle_command_camera(const mavlink_command_long_t &packet);
     MAV_RESULT handle_command_do_send_banner(const mavlink_command_long_t &packet);
-    MAV_RESULT handle_command_do_gripper(mavlink_command_long_t &packet);
+    MAV_RESULT handle_command_do_gripper(const mavlink_command_long_t &packet);
     MAV_RESULT handle_command_do_set_mode(const mavlink_command_long_t &packet);
     MAV_RESULT handle_command_get_home_position(const mavlink_command_long_t &packet);
 
@@ -392,7 +393,7 @@ private:
 
     virtual void        handleMessage(mavlink_message_t * msg) = 0;
 
-    MAV_RESULT handle_servorelay_message(mavlink_command_long_t &packet);
+    MAV_RESULT handle_servorelay_message(const mavlink_command_long_t &packet);
 
     bool calibrate_gyros();
 
diff --git a/libraries/GCS_MAVLink/GCS_Common.cpp b/libraries/GCS_MAVLink/GCS_Common.cpp
index 22068e7297..1c00185922 100644
--- a/libraries/GCS_MAVLink/GCS_Common.cpp
+++ b/libraries/GCS_MAVLink/GCS_Common.cpp
@@ -2318,6 +2318,10 @@ void GCS_MAVLINK::handle_common_message(mavlink_message_t *msg)
         handle_common_mission_message(msg);
         break;
 
+    case MAVLINK_MSG_ID_COMMAND_LONG:
+        handle_command_long(msg);
+        break;
+
     case MAVLINK_MSG_ID_COMMAND_INT:
         handle_command_int(msg);
         break;
@@ -2653,7 +2657,7 @@ MAV_RESULT GCS_MAVLINK::handle_command_get_home_position(const mavlink_command_l
     return MAV_RESULT_ACCEPTED;
 }
 
-MAV_RESULT GCS_MAVLINK::handle_command_do_gripper(mavlink_command_long_t &packet)
+MAV_RESULT GCS_MAVLINK::handle_command_do_gripper(const mavlink_command_long_t &packet)
 {
     AP_Gripper *gripper = AP::gripper();
     if (gripper == nullptr) {
@@ -2685,7 +2689,7 @@ MAV_RESULT GCS_MAVLINK::handle_command_do_gripper(mavlink_command_long_t &packet
     return result;
 }
 
-MAV_RESULT GCS_MAVLINK::handle_command_long_message(mavlink_command_long_t &packet)
+MAV_RESULT GCS_MAVLINK::handle_command_long_packet(const mavlink_command_long_t &packet)
 {
     MAV_RESULT result = MAV_RESULT_FAILED;
 
@@ -2773,6 +2777,18 @@ MAV_RESULT GCS_MAVLINK::handle_command_long_message(mavlink_command_long_t &pack
     return result;
 }
 
+void GCS_MAVLINK::handle_command_long(mavlink_message_t *msg)
+{
+    // decode packet
+    mavlink_command_long_t packet;
+    mavlink_msg_command_long_decode(msg, &packet);
+
+    const MAV_RESULT result = handle_command_long_packet(packet);
+
+    // send ACK or NAK
+    mavlink_msg_command_ack_send_buf(msg, chan, packet.command, result);
+}
+
 MAV_RESULT GCS_MAVLINK::handle_command_int_packet(const mavlink_command_int_t &packet)
 {
     return MAV_RESULT_UNSUPPORTED;
diff --git a/libraries/GCS_MAVLink/GCS_ServoRelay.cpp b/libraries/GCS_MAVLink/GCS_ServoRelay.cpp
index 466e905c61..e2e8a24a1d 100644
--- a/libraries/GCS_MAVLink/GCS_ServoRelay.cpp
+++ b/libraries/GCS_MAVLink/GCS_ServoRelay.cpp
@@ -2,7 +2,7 @@
 
 #include "AP_ServoRelayEvents/AP_ServoRelayEvents.h"
 
-MAV_RESULT GCS_MAVLINK::handle_servorelay_message(mavlink_command_long_t &packet)
+MAV_RESULT GCS_MAVLINK::handle_servorelay_message(const mavlink_command_long_t &packet)
 {
     AP_ServoRelayEvents *handler = AP::servorelayevents();
     if (handler == nullptr) {