diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py
index 9d9b3e2..a8e01bf 100644
--- a/Lib/unittest/mock.py
+++ b/Lib/unittest/mock.py
@@ -2265,7 +2265,12 @@ def _iterate_read_data(read_data):
     # Helper for mock_open:
     # Retrieve lines from read_data via a generator so that separate calls to
     # readline, read, and readlines are properly interleaved
-    data_as_list = ['{}\n'.format(l) for l in read_data.split('\n')]
+    newline = '\n'
+    if type(read_data) == bytes:
+        newline = b'\n'
+
+    data_as_list = ['{}\n'.format(l) for l in
+            read_data.split(newline)]
 
     if data_as_list[-1] == '\n':
         # If the last line ended in a newline, the list comprehension will have an
diff --git a/Lib/unittest/test/testmock/testmock.py b/Lib/unittest/test/testmock/testmock.py
index 3a104cb..a6c0893 100644
--- a/Lib/unittest/test/testmock/testmock.py
+++ b/Lib/unittest/test/testmock/testmock.py
@@ -8,7 +8,7 @@ from unittest.mock import (
     call, DEFAULT, patch, sentinel,
     MagicMock, Mock, NonCallableMock,
     NonCallableMagicMock, _CallList,
-    create_autospec
+    create_autospec, mock_open
 )
 
 
@@ -1444,5 +1444,11 @@ class MockTest(unittest.TestCase):
             mock.foo
 
 
+    def test_mock_open(self):
+        m = mock_open(read_data= b'abc')
+        with patch('%s.open' % __name__, m, create=True) :
+            with open('abc', 'rb') as f:
+                f.read()
+
 if __name__ == '__main__':
     unittest.main()