diff --git a/pyupgrade/_data.py b/pyupgrade/_data.py
index f9516df5..15e03a72 100644
--- a/pyupgrade/_data.py
+++ b/pyupgrade/_data.py
@@ -40,6 +40,7 @@ class State(NamedTuple):
     '__future__',
     'functools',
     'mmap',
+    'os',
     'select',
     'six',
     'six.moves',
diff --git a/pyupgrade/_plugins/oserror_aliases.py b/pyupgrade/_plugins/oserror_aliases.py
index 57d272b1..c11cadfd 100644
--- a/pyupgrade/_plugins/oserror_aliases.py
+++ b/pyupgrade/_plugins/oserror_aliases.py
@@ -17,7 +17,7 @@
 from pyupgrade._token_helpers import replace_name
 
 ERROR_NAMES = frozenset(('EnvironmentError', 'IOError', 'WindowsError'))
-ERROR_MODULES = frozenset(('mmap', 'select', 'socket'))
+ERROR_MODULES = frozenset(('mmap', 'select', 'socket', 'os'))
 
 
 def _fix_oserror_except(