diff --git a/libp2p-swarm/src/transport.rs b/libp2p-swarm/src/transport.rs
index 8bf8cf48f23..b38380018fb 100644
--- a/libp2p-swarm/src/transport.rs
+++ b/libp2p-swarm/src/transport.rs
@@ -35,7 +35,7 @@ use futures::future::{IntoFuture, Future, ok as future_ok, FutureResult};
 use multiaddr::Multiaddr;
 use multistream_select;
 use muxing::StreamMuxer;
-use std::io::{Cursor, Error as IoError, Read, Write};
+use std::io::{Cursor, Error as IoError, ErrorKind as IoErrorKind, Read, Write};
 use std::iter;
 use tokio_io::{AsyncRead, AsyncWrite};
 
@@ -556,7 +556,7 @@ impl<'a, T, C> UpgradedNode<T, C>
 				let iter = upgrade.protocol_names()
 					.map(|(name, id)| (name, <Bytes as PartialEq>::eq, id));
 				let negotiated = multistream_select::dialer_select_proto(connection, iter)
-					.map_err(|err| panic!("{:?}", err));      // TODO:
+					.map_err(|err| IoError::new(IoErrorKind::Other, err));
 				negotiated.map(|(upgrade_id, conn)| (upgrade_id, conn, upgrade))
 			})
 			.and_then(|(upgrade_id, connection, upgrade)| {
@@ -605,14 +605,12 @@ impl<'a, T, C> UpgradedNode<T, C>
 					(n, <Bytes as PartialEq>::eq, t)
 				}
 				let iter = upgrade.protocol_names().map(iter_map);
-				let negotiated = multistream_select::listener_select_proto(connection, iter)
-					.map_err(|err| panic!("{:?}", err));      // TODO:
+				let negotiated = multistream_select::listener_select_proto(connection, iter);
 				negotiated.map(move |(upgrade_id, conn)| (upgrade_id, conn, upgrade, client_addr))
-					.map_err(|_| panic!())    // TODO:
+					.map_err(|err| IoError::new(IoErrorKind::Other, err))
 			})
-			.map_err(|err| panic!("{:?}", err))      // TODO:
 			.and_then(|(upgrade_id, connection, upgrade, client_addr)| {
-				upgrade.upgrade(connection, upgrade_id).map(|c| (c, client_addr))
+				upgrade.upgrade(connection, upgrade_id).map(|s| (s, client_addr))
 			});
 
 		Ok((Box::new(stream), new_addr))
diff --git a/multistream-select/src/error.rs b/multistream-select/src/error.rs
index 84a26e097fe..8f8d5fa271c 100644
--- a/multistream-select/src/error.rs
+++ b/multistream-select/src/error.rs
@@ -21,6 +21,8 @@
 //! Main `ProtocolChoiceError` error.
 
 use protocol::MultistreamSelectError;
+use std::error;
+use std::fmt;
 use std::io::Error as IoError;
 
 /// Error that can happen when negotiating a protocol with the remote.
@@ -49,3 +51,36 @@ impl From<IoError> for ProtocolChoiceError {
 		MultistreamSelectError::from(err).into()
 	}
 }
+
+impl error::Error for ProtocolChoiceError {
+	#[inline]
+	fn description(&self) -> &str {
+		match *self {
+			ProtocolChoiceError::MultistreamSelectError(_) => {
+				"error in the protocol"
+			},
+			ProtocolChoiceError::UnexpectedMessage => {
+				"received a message from the remote that makes no sense in the current context"
+			},
+			ProtocolChoiceError::NoProtocolFound => {
+				"we don't support any protocol in common with the remote"
+			},
+		}
+	}
+
+	fn cause(&self) -> Option<&error::Error> {
+		match *self {
+			ProtocolChoiceError::MultistreamSelectError(ref err) => {
+				Some(err)
+			}
+			_ => None,
+		}
+	}
+}
+
+impl fmt::Display for ProtocolChoiceError {
+	#[inline]
+	fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+		write!(fmt, "{}", error::Error::description(self))
+	}
+}
diff --git a/multistream-select/src/protocol/error.rs b/multistream-select/src/protocol/error.rs
index 1c0ff25c249..ceaebab7331 100644
--- a/multistream-select/src/protocol/error.rs
+++ b/multistream-select/src/protocol/error.rs
@@ -20,6 +20,8 @@
 
 //! Contains the error structs for the low-level protocol handling.
 
+use std::error;
+use std::fmt;
 use std::io::Error as IoError;
 
 /// Error at the multistream-select layer of communication.
@@ -44,3 +46,39 @@ impl From<IoError> for MultistreamSelectError {
 		MultistreamSelectError::IoError(err)
 	}
 }
+
+impl error::Error for MultistreamSelectError {
+	#[inline]
+	fn description(&self) -> &str {
+		match *self {
+			MultistreamSelectError::IoError(_) => {
+				"I/O error"
+			},
+			MultistreamSelectError::FailedHandshake => {
+				"the remote doesn't use the same multistream-select protocol as we do"
+			},
+			MultistreamSelectError::UnknownMessage => {
+				"received an unknown message from the remote"
+			},
+			MultistreamSelectError::WrongProtocolName => {
+				"protocol names must always start with `/`, otherwise this error is returned"
+			},
+		}
+	}
+
+	fn cause(&self) -> Option<&error::Error> {
+		match *self {
+			MultistreamSelectError::IoError(ref err) => {
+				Some(err)
+			}
+			_ => None,
+		}
+	}
+}
+
+impl fmt::Display for MultistreamSelectError {
+	#[inline]
+	fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+		write!(fmt, "{}", error::Error::description(self))
+	}
+}