diff --git a/src/error.rs b/src/error.rs
index 0f2e64a99..3d24ecf4f 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -96,6 +96,9 @@ pub enum Error {
     #[error("Unsupported network transport: {0}")]
     UnsupportedTransport(String),
 
+    #[error("Unsupported network transport upgrade: {0}")]
+    UnsupportedTransportUpgrade(String),
+
     #[error("Connection failed")]
     ConnectFailed,
 
diff --git a/src/net3/acceptor.rs b/src/net3/acceptor.rs
index 8127fda4d..7d2c5d733 100644
--- a/src/net3/acceptor.rs
+++ b/src/net3/acceptor.rs
@@ -61,8 +61,7 @@ impl Acceptor {
                         let tls_listener = transport.upgrade_listener(listener)?.await?;
                         self.accept(Box::new(tls_listener), executor);
                     }
-                    // TODO hanle unsupported upgrade
-                    Some(_) => todo!(),
+                    Some(u) => return Err(Error::UnsupportedTransportUpgrade(u)),
                 }
             }
             TransportName::Tor(_upgrade) => todo!(),
diff --git a/src/net3/connector.rs b/src/net3/connector.rs
index 40340741d..2dcfc0db5 100644
--- a/src/net3/connector.rs
+++ b/src/net3/connector.rs
@@ -58,8 +58,7 @@ impl Connector {
                         let stream = transport.upgrade_dialer(stream?)?.await;
                         Channel::new(Box::new(stream?), connect_url).await
                     }
-                    // TODO hanle unsupported upgrade
-                    Some(_) => todo!(),
+                    Some(u) => return Err(Error::UnsupportedTransportUpgrade(u)),
                 };
 
                 Ok(channel)