diff --git a/libraries/AP_SerialManager/AP_SerialManager.cpp b/libraries/AP_SerialManager/AP_SerialManager.cpp
index 93e2f681a1..defa032b12 100644
--- a/libraries/AP_SerialManager/AP_SerialManager.cpp
+++ b/libraries/AP_SerialManager/AP_SerialManager.cpp
@@ -642,7 +642,7 @@ bool AP_SerialManager::protocol_match(enum SerialProtocol protocol1, enum Serial
 }
 
 // setup any special options
-void AP_SerialManager::set_options(uint8_t i)
+void AP_SerialManager::set_options(uint16_t i)
 {
     struct UARTState &opt = state[i];
     // pass through to HAL
diff --git a/libraries/AP_SerialManager/AP_SerialManager.h b/libraries/AP_SerialManager/AP_SerialManager.h
index f0517bf167..779909203b 100644
--- a/libraries/AP_SerialManager/AP_SerialManager.h
+++ b/libraries/AP_SerialManager/AP_SerialManager.h
@@ -123,6 +123,7 @@ public:
         SerialProtocol_WindVane = 21,
         SerialProtocol_SLCAN = 22,
         SerialProtocol_RCIN = 23,
+        SerialProtocol_Hott = 27,
     };
 
     // get singleton instance
@@ -197,7 +198,7 @@ private:
     bool protocol_match(enum SerialProtocol protocol1, enum SerialProtocol protocol2) const;
 
     // setup any special options
-    void set_options(uint8_t i);
+    void set_options(uint16_t i);
 };
 
 namespace AP {