diff --git a/mitmproxy/connections.py b/mitmproxy/connections.py
index fc6374204..9c4bca2f0 100644
--- a/mitmproxy/connections.py
+++ b/mitmproxy/connections.py
@@ -6,6 +6,7 @@ import os
 from mitmproxy import stateobject
 from mitmproxy import certs
 from mitmproxy.net import tcp
+from mitmproxy.utils import strutils
 
 
 class ClientConnection(tcp.BaseHandler, stateobject.StateObject):
@@ -52,9 +53,15 @@ class ClientConnection(tcp.BaseHandler, stateobject.StateObject):
         return bool(self.connection) and not self.finished
 
     def __repr__(self):
+        if self.alpn_proto_negotiated:
+            alpn = "[ALPN: {}] ".format(
+                strutils.bytes_to_escaped_str(self.alpn_proto_negotiated)
+            )
+        else:
+            alpn = ""
         return "<ClientConnection: {ssl}{alpn}{address}>".format(
             ssl="[ssl] " if self.ssl_established else "",
-            alpn="[ALPN: {}] ".format(self.alpn_proto_negotiated) if self.alpn_proto_negotiated else "",
+            alpn=alpn,
             address=repr(self.address)
         )
 
@@ -71,7 +78,7 @@ class ClientConnection(tcp.BaseHandler, stateobject.StateObject):
         timestamp_end=float,
         sni=str,
         cipher_name=str,
-        alpn_proto_negotiated=str,
+        alpn_proto_negotiated=bytes,
         tls_version=str,
     )
 
@@ -162,9 +169,15 @@ class ServerConnection(tcp.TCPClient, stateobject.StateObject):
             ssl = "[ssl] "
         else:
             ssl = ""
+        if self.alpn_proto_negotiated:
+            alpn = "[ALPN: {}] ".format(
+                strutils.bytes_to_escaped_str(self.alpn_proto_negotiated)
+            )
+        else:
+            alpn = ""
         return "<ServerConnection: {ssl}{alpn}{address}>".format(
             ssl=ssl,
-            alpn="[ALPN: {}] ".format(self.alpn_proto_negotiated) if self.alpn_proto_negotiated else "",
+            alpn=alpn,
             address=repr(self.address)
         )
 
@@ -179,7 +192,7 @@ class ServerConnection(tcp.TCPClient, stateobject.StateObject):
         ssl_established=bool,
         cert=certs.SSLCert,
         sni=str,
-        alpn_proto_negotiated=str,
+        alpn_proto_negotiated=bytes,
         timestamp_start=float,
         timestamp_tcp_setup=float,
         timestamp_ssl_setup=float,
diff --git a/mitmproxy/test/tflow.py b/mitmproxy/test/tflow.py
index f100f62ed..959c9a2c3 100644
--- a/mitmproxy/test/tflow.py
+++ b/mitmproxy/test/tflow.py
@@ -72,7 +72,7 @@ def tclient_conn():
         timestamp_end=3,
         sni="address",
         cipher_name="cipher",
-        alpn_proto_negotiated=None,
+        alpn_proto_negotiated=b"http/1.1",
         tls_version="TLSv1.2",
     ))
     c.reply = controller.DummyReply()
diff --git a/mitmproxy/tools/console/flowdetailview.py b/mitmproxy/tools/console/flowdetailview.py
index 8c08d6eef..571a5e1b6 100644
--- a/mitmproxy/tools/console/flowdetailview.py
+++ b/mitmproxy/tools/console/flowdetailview.py
@@ -2,6 +2,7 @@ import urwid
 
 from mitmproxy.tools.console import common, searchable
 from mitmproxy.utils import human
+from mitmproxy.utils import strutils
 
 
 def maybe_timestamp(base, attr):
@@ -77,7 +78,7 @@ def flowdetails(state, flow):
                 parts.append(
                     [
                         "Alt names",
-                        ", ".join(str(x) for x in c.altnames)
+                        ", ".join(strutils.bytes_to_escaped_str(x) for x in c.altnames)
                     ]
                 )
             text.extend(
diff --git a/mitmproxy/tools/web/app.py b/mitmproxy/tools/web/app.py
index ce18c6f06..c0de4c1f4 100644
--- a/mitmproxy/tools/web/app.py
+++ b/mitmproxy/tools/web/app.py
@@ -34,6 +34,12 @@ def flow_to_json(flow: mitmproxy.flow.Flow) -> dict:
         "type": flow.type,
         "modified": flow.modified(),
     }
+    # .alpn_proto_negotiated is bytes, we need to decode that.
+    for conn in "client_conn", "server_conn":
+        if f[conn]["alpn_proto_negotiated"] is None:
+            continue
+        f[conn]["alpn_proto_negotiated"] = \
+            f[conn]["alpn_proto_negotiated"].decode(errors="backslashreplace")
     if flow.error:
         f["error"] = flow.error.get_state()