diff --git a/requires/development.txt b/requires/development.txt
index 314c854..6bd8b2d 100644
--- a/requires/development.txt
+++ b/requires/development.txt
@@ -1,5 +1,6 @@
 -r requires/installation.txt
 -r requires/testing.txt
+-e .
 
 flake8
 sphinx>=1.2,<2
diff --git a/requires/installation.txt b/requires/installation.txt
index ed4008b..44d8d5a 100644
--- a/requires/installation.txt
+++ b/requires/installation.txt
@@ -1 +1 @@
-tornado>=4.0,<6.1
+tornado>=4.3,<7
diff --git a/sprockets/mixins/correlation/mixins.py b/sprockets/mixins/correlation/mixins.py
index fba8d6c..7703ec6 100644
--- a/sprockets/mixins/correlation/mixins.py
+++ b/sprockets/mixins/correlation/mixins.py
@@ -46,7 +46,7 @@ class HandlerMixin(object):
         # one exists.  We also want to set it in the outgoing response
         # which the property setter does for us.
         maybe_future = super(HandlerMixin, self).prepare()
-        if concurrent.is_future(maybe_future):  # pragma: nocover
+        if concurrent.is_future(maybe_future):
             await maybe_future
 
         correlation_id = self.get_request_header(self.__header_name, None)
diff --git a/tests.py b/tests.py
index a279fff..d5877b2 100644
--- a/tests.py
+++ b/tests.py
@@ -57,11 +57,11 @@ class CorrelationIDLoggerTests(testing.AsyncHTTPTestCase):
         self.patcher = unittest.mock.patch(
             'sprockets.mixins.correlation.mixins.log.access_log')
         self.access_logger = self.patcher.start()
-        super(CorrelationIDLoggerTests, self).setUp()
+        super().setUp()
 
     def tearDown(self):
         self.patcher.stop()
-        super(CorrelationIDLoggerTests, self).tearDown()
+        super().tearDown()
 
     def test_lt_400_logs_info(self):
         for status in (200, 202):
diff --git a/tox.ini b/tox.ini
index 77ff7ee..713c902 100644
--- a/tox.ini
+++ b/tox.ini
@@ -22,4 +22,4 @@ deps =
 [testenv:tornado6]
 deps =
 	-r requires/testing.txt
-	tornado>=6,<6.1
+	tornado>=6,<7