diff --git a/flake8/engine.py b/flake8/engine.py
index 9cbdf6d..0f440c1 100644
--- a/flake8/engine.py
+++ b/flake8/engine.py
@@ -120,7 +120,8 @@ class StyleGuide(object):
     ])
 
     def __init__(self, **kwargs):
-        self._styleguide = NoQAStyleGuide(**kwargs)
+        # This allows us to inject a mocked StyleGuide in the tests.
+        self._styleguide = kwargs.pop('styleguide', NoQAStyleGuide(**kwargs))
 
     @property
     def options(self):
@@ -139,8 +140,8 @@ class StyleGuide(object):
         """
         try:
             return func(*args, **kwargs)
-        except IOError as ioerr:
-            if ioerr.errno in self.serial_retry_errors:
+        except OSError as oserr:
+            if oserr.errno in self.serial_retry_errors:
                 self.init_report(pep8.StandardReport)
             else:
                 raise
@@ -161,7 +162,7 @@ class StyleGuide(object):
             filename=filename,
             lines=lines,
             expected=expected,
-            line_offset=0,
+            line_offset=line_offset,
         )
 
 
diff --git a/flake8/tests/test_engine.py b/flake8/tests/test_engine.py
index 60b388c..a6faab5 100644
--- a/flake8/tests/test_engine.py
+++ b/flake8/tests/test_engine.py
@@ -1,5 +1,6 @@
 from __future__ import with_statement
 
+import errno
 import unittest
 try:
     from unittest import mock
@@ -7,6 +8,7 @@ except ImportError:
     import mock  # < PY33
 
 from flake8 import engine, util, __version__, reporter
+import pep8
 
 
 class TestEngine(unittest.TestCase):
@@ -112,5 +114,87 @@ class TestEngine(unittest.TestCase):
             assert 'X' not in sg.options.ignore
 
 
+def oserror_generator(error_number, message='Ominous OSError message'):
+    def oserror_side_effect(*args, **kwargs):
+        if hasattr(oserror_side_effect, 'used'):
+            return
+
+        oserror_side_effect.used = True
+        raise OSError(error_number, message)
+
+    return oserror_side_effect
+
+
+class TestStyleGuide(unittest.TestCase):
+    def setUp(self):
+        mocked_styleguide = mock.Mock(spec=engine.NoQAStyleGuide)
+        self.styleguide = engine.StyleGuide(styleguide=mocked_styleguide)
+        self.mocked_sg = mocked_styleguide
+
+    def test_proxies_excluded(self):
+        self.styleguide.excluded('file.py', parent='.')
+
+        self.mocked_sg.excluded.assert_called_once_with('file.py', parent='.')
+
+    def test_proxies_init_report(self):
+        reporter = object()
+        self.styleguide.init_report(reporter)
+
+        self.mocked_sg.init_report.assert_called_once_with(reporter)
+
+    def test_proxies_check_files(self):
+        self.styleguide.check_files(['foo', 'bar'])
+
+        self.mocked_sg.check_files.assert_called_once_with(
+            paths=['foo', 'bar']
+        )
+
+    def test_proxies_input_file(self):
+        self.styleguide.input_file('file.py',
+                                   lines=[9, 10],
+                                   expected='foo',
+                                   line_offset=20)
+
+        self.mocked_sg.input_file.assert_called_once_with(filename='file.py',
+                                                          lines=[9, 10],
+                                                          expected='foo',
+                                                          line_offset=20)
+
+    def test_check_files_retries_on_specific_OSErrors(self):
+        self.mocked_sg.check_files.side_effect = oserror_generator(
+            errno.ENOSPC, 'No space left on device'
+        )
+
+        self.styleguide.check_files(['foo', 'bar'])
+
+        self.mocked_sg.init_report.assert_called_once_with(pep8.StandardReport)
+
+    def test_input_file_retries_on_specific_OSErrors(self):
+        self.mocked_sg.input_file.side_effect = oserror_generator(
+            errno.ENOSPC, 'No space left on device'
+        )
+
+        self.styleguide.input_file('file.py')
+
+        self.mocked_sg.init_report.assert_called_once_with(pep8.StandardReport)
+
+    def test_check_files_reraises_unknown_OSErrors(self):
+        self.mocked_sg.check_files.side_effect = oserror_generator(
+            errno.EADDRINUSE,
+            'lol why are we talking about binding to sockets'
+        )
+
+        self.assertRaises(OSError, self.styleguide.check_files,
+                          ['foo', 'bar'])
+
+    def test_input_file_reraises_unknown_OSErrors(self):
+        self.mocked_sg.input_file.side_effect = oserror_generator(
+            errno.EADDRINUSE,
+            'lol why are we talking about binding to sockets'
+        )
+
+        self.assertRaises(OSError, self.styleguide.input_file,
+                          ['foo', 'bar'])
+
 if __name__ == '__main__':
     unittest.main()