diff --git a/src/trx-server/trx-backend/trx-backend-ft450d/src/lib.rs b/src/trx-server/trx-backend/trx-backend-ft450d/src/lib.rs
index e7d612e..9450ac5 100644
--- a/src/trx-server/trx-backend/trx-backend-ft450d/src/lib.rs
+++ b/src/trx-server/trx-backend/trx-backend-ft450d/src/lib.rs
@@ -519,6 +519,7 @@ fn encode_mode(mode: &RigMode) -> DynResult<char> {
         RigMode::CWR => Ok('7'),
         RigMode::PKT => Ok('9'),
         RigMode::WFM => Ok('4'),
+        RigMode::AMC => Err("Unsupported mode for FT-450D".into()),
         RigMode::Other(_) => Err("Unsupported mode for FT-450D".into()),
     }
 }