diff --git a/.flake8 b/.flake8
index 659394c8..343e13a4 100644
--- a/.flake8
+++ b/.flake8
@@ -4,10 +4,13 @@ show-source = True
 
 select = E,F,W,C,I,B,S,T,Q,N400
 ignore = S101,S608
+extend-ignore = F821,E721
 per-file-ignores =
     tests/test_init_import.py:F401
     tests/conftest.py:S311
     axion/handler/__init__.py:F811
+builtins =
+    _,
 
 import-order-style=appnexus
 application-package-names=axion
@@ -18,7 +21,6 @@ hang-closing = false
 max-line-length = 90
 inline-quotes = single
 
-disable-noqa = True
 exclude =
     .git,
     __pycache__,
diff --git a/axion/handler/analysis/return_type.py b/axion/handler/analysis/return_type.py
index 53dbcc93..47c9cabc 100644
--- a/axion/handler/analysis/return_type.py
+++ b/axion/handler/analysis/return_type.py
@@ -90,7 +90,7 @@ def _analyze_headers(
         elif not types.is_dict_like(headers):
             return {
                 exceptions.Error(
-                    param_name=f'return.headers',
+                    param_name='return.headers',
                     reason=exceptions.IncorrectTypeReason(
                         expected=model.COOKIES_HEADERS_TYPE,
                         actual=headers,
@@ -115,7 +115,7 @@ def _analyze_cookies(
         elif not types.is_dict_like(cookies):
             return {
                 exceptions.Error(
-                    param_name=f'return.cookies',
+                    param_name='return.cookies',
                     reason=exceptions.IncorrectTypeReason(
                         expected=model.COOKIES_HEADERS_TYPE,
                         actual=cookies,
diff --git a/axion/oas/parser/type.py b/axion/oas/parser/type.py
index e7e3cb5c..abee5778 100644
--- a/axion/oas/parser/type.py
+++ b/axion/oas/parser/type.py
@@ -381,7 +381,7 @@ def _resolve_oas_string(
         if min_length is not None and max_length is not None:
             if min_length > max_length:
                 raise exceptions.OASInvalidConstraints(
-                    f'type=string cannot have max_length < min_length. ',
+                    'type=string cannot have max_length < min_length. ',
                     f'min_length={min_length} '
                     f'max_length={max_length}.',
                 )
diff --git a/axion/utils/types.py b/axion/utils/types.py
index eaa60c4a..7b2df66d 100644
--- a/axion/utils/types.py
+++ b/axion/utils/types.py
@@ -43,7 +43,7 @@ def is_new_type(tt: t.Type[t.Any]) -> bool:
 
 @functools.lru_cache(maxsize=30, typed=True)
 def is_none_type(tt: t.Type[t.Any]) -> bool:
-    return tt is type(None)  # noqa
+    return tt is type(None)
 
 
 @functools.lru_cache(maxsize=30, typed=True)
diff --git a/requirements/flake8.txt b/requirements/flake8.txt
index 0caa162d..aed8cbc2 100644
--- a/requirements/flake8.txt
+++ b/requirements/flake8.txt
@@ -1,4 +1,4 @@
-flake8==3.7.9
+flake8==3.8.1
 flake8-import-order==0.18.1
 flake8-bugbear==20.1.4
 flake8-commas==2.0.0
diff --git a/tests/test_oas_mixed_type.py b/tests/test_oas_mixed_type.py
index 0c754197..b6484933 100644
--- a/tests/test_oas_mixed_type.py
+++ b/tests/test_oas_mixed_type.py
@@ -768,17 +768,17 @@ def _do() -> t.Any:
                 raise AssertionError('This should not happen')
         elif isinstance(ap_1, bool) and isinstance(ap_2, dict):
             assert (
-                f'additionalProperties value differs between mixed schemas. '
-                f'a=bool != b=dict. When using "anyOf,oneOf,allOf" values in '
-                f'same location must be equal. '
-                f'Either make it so or remove one of the duplicating properties.'
+                'additionalProperties value differs between mixed schemas. '
+                'a=bool != b=dict. When using "anyOf,oneOf,allOf" values in '
+                'same location must be equal. '
+                'Either make it so or remove one of the duplicating properties.'
             ) == str(err.value)
         elif isinstance(ap_1, dict) and isinstance(ap_2, bool):
             assert (
-                f'additionalProperties value differs between mixed schemas. '
-                f'a=dict != b=bool. When using "anyOf,oneOf,allOf" values in '
-                f'same location must be equal. '
-                f'Either make it so or remove one of the duplicating properties.'
+                'additionalProperties value differs between mixed schemas. '
+                'a=dict != b=bool. When using "anyOf,oneOf,allOf" values in '
+                'same location must be equal. '
+                'Either make it so or remove one of the duplicating properties.'
             ) == str(err.value)
         else:
             raise AssertionError('This should not happen')