diff --git a/libraries/AP_SerialManager/AP_SerialManager.h b/libraries/AP_SerialManager/AP_SerialManager.h
index b548656297f91..30bae549f6b87 100644
--- a/libraries/AP_SerialManager/AP_SerialManager.h
+++ b/libraries/AP_SerialManager/AP_SerialManager.h
@@ -80,6 +80,7 @@ class AP_SerialManager {
         SerialProtocol_Tramp = 44,
         SerialProtocol_DDS_XRCE = 45,
         SerialProtocol_IMUOUT = 46,
+        // Reserving Serial Protocol 47 for SerialProtocol_IQ
         SerialProtocol_NumProtocols                    // must be the last value
     };