diff --git a/libraries/AP_SerialManager/AP_SerialManager.cpp b/libraries/AP_SerialManager/AP_SerialManager.cpp
index a42de342ab..b94ba06c29 100644
--- a/libraries/AP_SerialManager/AP_SerialManager.cpp
+++ b/libraries/AP_SerialManager/AP_SerialManager.cpp
@@ -541,6 +541,8 @@ void AP_SerialManager::init()
                 case SerialProtocol_RCIN:
                     if (!AP::RC().has_uart()) {
                         AP::RC().add_uart(uart);
+                    } else {
+                        GCS_SEND_TEXT(MAV_SEVERITY_WARNING, "SERIAL%u_PROTOCOL - uart already added", i);
                     }
 
                     break;