diff --git a/libraries/GCS_MAVLink/GCS.h b/libraries/GCS_MAVLink/GCS.h
index 113bca160a..c0a29fba23 100644
--- a/libraries/GCS_MAVLink/GCS.h
+++ b/libraries/GCS_MAVLink/GCS.h
@@ -297,7 +297,7 @@ public:
     void        update_receive(uint32_t max_time_us=1000);
     void        update_send();
     void        init(AP_HAL::UARTDriver *port, mavlink_channel_t mav_chan);
-    void        setup_uart(const AP_SerialManager& serial_manager, AP_SerialManager::SerialProtocol protocol, uint8_t instance);
+    void        setup_uart(AP_SerialManager::SerialProtocol protocol, uint8_t instance);
     void        send_message(enum ap_message id);
     void        send_text(MAV_SEVERITY severity, const char *fmt, ...) const;
     void        send_textv(MAV_SEVERITY severity, const char *fmt, va_list arg_list) const;
@@ -964,7 +964,7 @@ public:
 
     void update_send();
     void update_receive();
-    virtual void setup_uarts(AP_SerialManager &serial_manager);
+    virtual void setup_uarts();
 
     bool out_of_time() const {
         return _out_of_time;
diff --git a/libraries/GCS_MAVLink/GCS_Common.cpp b/libraries/GCS_MAVLink/GCS_Common.cpp
index dc436d7e34..93e3b7ec44 100644
--- a/libraries/GCS_MAVLink/GCS_Common.cpp
+++ b/libraries/GCS_MAVLink/GCS_Common.cpp
@@ -105,10 +105,10 @@ GCS_MAVLINK::init(AP_HAL::UARTDriver *port, mavlink_channel_t mav_chan)
   setup a UART, handling begin() and init()
  */
 void
-GCS_MAVLINK::setup_uart(const AP_SerialManager& serial_manager, AP_SerialManager::SerialProtocol protocol, uint8_t instance)
+GCS_MAVLINK::setup_uart(AP_SerialManager::SerialProtocol protocol, uint8_t instance)
 {
     // search for serial port
-    
+    const AP_SerialManager& serial_manager = AP::serialmanager();
     AP_HAL::UARTDriver *uart;
     uart = serial_manager.find_serial(protocol, instance);
     if (uart == nullptr) {
@@ -2270,10 +2270,10 @@ void GCS::send_mission_item_reached_message(uint16_t mission_index)
     }
 }
 
-void GCS::setup_uarts(AP_SerialManager &serial_manager)
+void GCS::setup_uarts()
 {
     for (uint8_t i = 1; i < MAVLINK_COMM_NUM_BUFFERS; i++) {
-        chan(i).setup_uart(serial_manager, AP_SerialManager::SerialProtocol_MAVLink, i);
+        chan(i).setup_uart(AP_SerialManager::SerialProtocol_MAVLink, i);
     }
 
     frsky.init();