diff --git a/.travis.yml b/.travis.yml
index 20afc279e..44d452c27 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -52,7 +52,6 @@ matrix:
         - wget https://github.com/gohugoio/hugo/releases/download/v0.41/hugo_0.41_Linux-64bit.deb
         - sudo dpkg -i hugo*.deb
         - pip install tox virtualenv setuptools
-        - pyenv global system 3.6
       script:
         - tox
       after_success:
diff --git a/mitmproxy/contentviews/base.py b/mitmproxy/contentviews/base.py
index 6072dfb76..9b34f3d4a 100644
--- a/mitmproxy/contentviews/base.py
+++ b/mitmproxy/contentviews/base.py
@@ -37,7 +37,7 @@ class View:
 
 def format_pairs(
         items: typing.Iterable[typing.Tuple[TTextType, TTextType]]
-)-> typing.Iterator[TViewLine]:
+) -> typing.Iterator[TViewLine]:
 
     """
     Helper function that accepts a list of (k,v) pairs into a list of
diff --git a/mitmproxy/contentviews/image/image_parser.py b/mitmproxy/contentviews/image/image_parser.py
index fcc50cb5b..d5bb404f9 100644
--- a/mitmproxy/contentviews/image/image_parser.py
+++ b/mitmproxy/contentviews/image/image_parser.py
@@ -54,7 +54,7 @@ def parse_gif(data: bytes) -> Metadata:
         entries = block.body.body.entries
         for entry in entries:
             comment = entry.bytes
-            if comment is not b'':
+            if comment != b'':
                 parts.append(('comment', str(comment)))
     return parts
 
diff --git a/setup.py b/setup.py
index 7f83de631..50d02a55a 100644
--- a/setup.py
+++ b/setup.py
@@ -88,7 +88,7 @@ setup(
         ],
         'dev': [
             "asynctest>=0.12.0",
-            "flake8>=3.5,<3.7",
+            "flake8>=3.5,<=3.7.8",
             "Flask>=1.0,<1.1",
             "mypy>=0.590,<0.591",
             "parver>=0.1,<2.0",
diff --git a/test/mitmproxy/addons/test_view.py b/test/mitmproxy/addons/test_view.py
index 976c14b79..f5088a689 100644
--- a/test/mitmproxy/addons/test_view.py
+++ b/test/mitmproxy/addons/test_view.py
@@ -471,7 +471,7 @@ def test_focus():
     v = view.View()
     v.add([tft()])
     f = view.Focus(v)
-    assert f.index is 0
+    assert f.index == 0
     assert f.flow is v[0]
 
     # Start empty
diff --git a/test/mitmproxy/script/test_concurrent.py b/test/mitmproxy/script/test_concurrent.py
index 3ec58760f..70d41511e 100644
--- a/test/mitmproxy/script/test_concurrent.py
+++ b/test/mitmproxy/script/test_concurrent.py
@@ -43,17 +43,17 @@ class TestConcurrent(tservers.MasterTest):
             assert await tctx.master.await_log("decorator not supported")
 
     def test_concurrent_class(self, tdata):
-            with taddons.context() as tctx:
-                sc = tctx.script(
-                    tdata.path(
-                        "mitmproxy/data/addonscripts/concurrent_decorator_class.py"
-                    )
+        with taddons.context() as tctx:
+            sc = tctx.script(
+                tdata.path(
+                    "mitmproxy/data/addonscripts/concurrent_decorator_class.py"
                 )
-                f1, f2 = tflow.tflow(), tflow.tflow()
-                tctx.cycle(sc, f1)
-                tctx.cycle(sc, f2)
-                start = time.time()
-                while time.time() - start < 5:
-                    if f1.reply.state == f2.reply.state == "committed":
-                        return
-                raise ValueError("Script never acked")
+            )
+            f1, f2 = tflow.tflow(), tflow.tflow()
+            tctx.cycle(sc, f1)
+            tctx.cycle(sc, f2)
+            start = time.time()
+            while time.time() - start < 5:
+                if f1.reply.state == f2.reply.state == "committed":
+                    return
+            raise ValueError("Script never acked")