diff --git a/plugins/plugin_utils/compat/telnetlib.py b/plugins/plugin_utils/compat/telnetlib.py
index 9472a3014..892d82970 100644
--- a/plugins/plugin_utils/compat/telnetlib.py
+++ b/plugins/plugin_utils/compat/telnetlib.py
@@ -513,7 +513,7 @@ def rawq_getchar(self):
             self.fill_rawq()
             if self.eof:
                 raise EOFError
-        c = self.rawq[self.irawq : self.irawq + 1]
+        c = self.rawq[self.irawq : self.irawq + 1]  # noqa: E203
         self.irawq = self.irawq + 1
         if self.irawq >= len(self.rawq):
             self.rawq = b""
diff --git a/tox.ini b/tox.ini
index 14db05a79..7071bf976 100644
--- a/tox.ini
+++ b/tox.ini
@@ -21,3 +21,12 @@ commands =
 
 [testenv:venv]
 commands = {posargs}
+
+[flake8]
+# E123, E125 skipped as they are invalid PEP-8.
+
+show-source = True
+ignore = E123,E125,E203,E402,E501,E741,F401,F811,F841,W503
+max-line-length = 160
+builtins = _
+exclude = .git,.tox,tests/unit/compat/