diff --git a/mitmproxy/addons/core.py b/mitmproxy/addons/core.py
index b0d8ee275..33d672790 100644
--- a/mitmproxy/addons/core.py
+++ b/mitmproxy/addons/core.py
@@ -112,7 +112,7 @@ class Core:
         val = sval  # type: typing.Union[int, str]
         if spec == "status_code":
             try:
-                val = int(val)
+                val = int(val)  # type: ignore
             except ValueError as v:
                 raise exceptions.CommandError(
                     "Status code is not an integer: %s" % val
@@ -145,7 +145,7 @@ class Core:
                 if spec == "status_code":
                     resp.status_code = val
                     if val in status_codes.RESPONSES:
-                        resp.reason = status_codes.RESPONSES[int(val)]
+                        resp.reason = status_codes.RESPONSES[val]  # type: ignore
                 elif spec == "reason":
                     resp.reason = val
                 else:
diff --git a/mitmproxy/eventsequence.py b/mitmproxy/eventsequence.py
index 68d97a23b..d263727b7 100644
--- a/mitmproxy/eventsequence.py
+++ b/mitmproxy/eventsequence.py
@@ -1,8 +1,8 @@
 import typing
 
 from mitmproxy import controller
-from mitmproxy import http
 from mitmproxy import flow
+from mitmproxy import http
 from mitmproxy import tcp
 from mitmproxy import websocket
 
@@ -40,8 +40,10 @@ Events = frozenset([
     "update",
 ])
 
+TEventGenerator = typing.Iterator[typing.Tuple[str, typing.Any]]
 
-def _iterate_http(f: http.HTTPFlow):
+
+def _iterate_http(f: http.HTTPFlow) -> TEventGenerator:
     if f.request:
         yield "requestheaders", f
         yield "request", f
@@ -52,7 +54,7 @@ def _iterate_http(f: http.HTTPFlow):
         yield "error", f
 
 
-def _iterate_websocket(f: websocket.WebSocketFlow):
+def _iterate_websocket(f: websocket.WebSocketFlow) -> TEventGenerator:
     messages = f.messages
     f.messages = []
     f.reply = controller.DummyReply()
@@ -65,7 +67,7 @@ def _iterate_websocket(f: websocket.WebSocketFlow):
     yield "websocket_end", f
 
 
-def _iterate_tcp(f: tcp.TCPFlow):
+def _iterate_tcp(f: tcp.TCPFlow) -> TEventGenerator:
     messages = f.messages
     f.messages = []
     f.reply = controller.DummyReply()
@@ -78,19 +80,17 @@ def _iterate_tcp(f: tcp.TCPFlow):
     yield "tcp_end", f
 
 
-TEventGenerator = typing.Iterator[typing.Tuple[str, typing.Any]]
-
 _iterate_map = {
     http.HTTPFlow: _iterate_http,
     websocket.WebSocketFlow: _iterate_websocket,
-    tcp.TCPFlow: _iterate_tcp
-}  # type: typing.Dict[typing.Type[flow.Flow], typing.Callable[[flow.Flow], TEventGenerator]]
+    tcp.TCPFlow: _iterate_tcp,
+}  # type: typing.Dict[typing.Type[flow.Flow], typing.Callable[[typing.Any], TEventGenerator]]
 
 
 def iterate(f: flow.Flow) -> TEventGenerator:
     try:
         e = _iterate_map[type(f)]
-    except KeyError as e:
-        raise TypeError("Unknown flow type: {}".format(f)) from e
+    except KeyError as err:
+        raise TypeError("Unknown flow type: {}".format(f)) from err
     else:
         yield from e(f)
diff --git a/mitmproxy/utils/human.py b/mitmproxy/utils/human.py
index b3934846c..d67fb3104 100644
--- a/mitmproxy/utils/human.py
+++ b/mitmproxy/utils/human.py
@@ -71,7 +71,7 @@ def format_address(address: tuple) -> str:
     """
     try:
         host = ipaddress.ip_address(address[0])
-        if host.version == 4:
+        if isinstance(host, ipaddress.IPv4Address):
             return "{}:{}".format(str(host), address[1])
         # If IPv6 is mapped to IPv4
         elif host.ipv4_mapped:
diff --git a/setup.py b/setup.py
index 212ad95ea..441a1d8f9 100644
--- a/setup.py
+++ b/setup.py
@@ -90,7 +90,7 @@ setup(
         'dev': [
             "flake8>=3.2.1, <3.4",
             "Flask>=0.10.1, <0.13",
-            "mypy>=0.501, <0.512",
+            "mypy>=0.501, <0.521",
             "pytest-cov>=2.2.1, <3",
             "pytest-faulthandler>=1.3.0, <2",
             "pytest-timeout>=1.0.0, <2",