diff --git a/keystone/tests/unit/identity/test_core.py b/keystone/tests/unit/identity/test_core.py
index f69b367df9..fc006054c1 100644
--- a/keystone/tests/unit/identity/test_core.py
+++ b/keystone/tests/unit/identity/test_core.py
@@ -105,8 +105,8 @@ class TestDomainConfigs(unit.BaseTestCase):
                 name,
                 identity.DOMAIN_CONF_FTAIL)))
 
-        walk_fake = lambda *a, **kwa: (
-            ('/fake/keystone/domains/config', [], files), )
+        def walk_fake(*a, **kwa):
+            return ('/fake/keystone/domains/config', [], files),
 
         generic_driver = mock.Mock(is_sql=False)
 
diff --git a/keystone/tests/unit/test_backend_templated.py b/keystone/tests/unit/test_backend_templated.py
index 01c7e36cb3..096d5cb029 100644
--- a/keystone/tests/unit/test_backend_templated.py
+++ b/keystone/tests/unit/test_backend_templated.py
@@ -88,7 +88,8 @@ class TestTemplatedCatalog(unit.TestCase, catalog_tests.CatalogTests):
             "Templated backend doesn't have disabled endpoints")
 
     def assert_catalogs_equal(self, expected, observed):
-        sort_key = lambda d: d['id']
+        def sort_key(d):
+            return d['id']
         for e, o in zip(sorted(expected, key=sort_key),
                         sorted(observed, key=sort_key)):
             expected_endpoints = e.pop('endpoints')
diff --git a/tools/fast8.sh b/tools/fast8.sh
index 97ab09f19b..dbe8536662 100755
--- a/tools/fast8.sh
+++ b/tools/fast8.sh
@@ -22,4 +22,4 @@ for FILE in $CHANGED; do
     fi
 done
 
-diff -u --from-file /dev/null $CHECK | flake8 --diff --ignore=D100,D101,D102,D103,D104,E305,E402,E501,W503,W504,W605,E731
+diff -u --from-file /dev/null $CHECK | flake8 --diff --ignore=D100,D101,D102,D103,D104,E305,E402,E501,W503,W504,W605
diff --git a/tox.ini b/tox.ini
index 2becb181cc..bf92e32421 100644
--- a/tox.ini
+++ b/tox.ini
@@ -32,7 +32,7 @@ deps =
      .[bandit]
      {[testenv]deps}
 commands =
-  flake8 --ignore=D100,D101,D102,D103,D104,E305,E402,E501,W503,W504,W605,E731
+  flake8 --ignore=D100,D101,D102,D103,D104,E305,E402,E501,W503,W504,W605
   # Run bash8 during pep8 runs to ensure violations are caught by
   # the check and gate queues
   bashate devstack/plugin.sh
@@ -127,8 +127,7 @@ enable-extensions = H203,H904
 # TODO(wxy): Fix the pep8 issue.
 # E402: module level import not at top of file
 # W503: line break before binary operator
-# E731: do not assign a lambda expression, use a def
-ignore = D100,D101,D102,D103,D104,D203,E402,W503,E731
+ignore = D100,D101,D102,D103,D104,D203,E402,W503
 
 exclude=.venv,.git,.tox,build,dist,*lib/python*,*egg,tools,vendor,.update-venv,*.ini,*.po,*.pot
 max-complexity=24