diff --git a/Lib/codecs.py b/Lib/codecs.py
index 6b028adb1d28e6..884be0b2c02e43 100644
--- a/Lib/codecs.py
+++ b/Lib/codecs.py
@@ -838,7 +838,7 @@ def write(self, data):
 
     def writelines(self, list):
 
-        data = ''.join(list)
+        data = b''.join(list)
         data, bytesdecoded = self.decode(data, self.errors)
         return self.writer.write(data)
 
diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index 8c14f5981d0bce..f665febfc90a21 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -3146,6 +3146,27 @@ def test_decode(self):
                 self.assertEqual(data.decode('latin1'), expected)
 
 
+class StreamRecoderTest(unittest.TestCase):
+    def test_writelines(self):
+        bio = io.BytesIO()
+        codec = codecs.lookup('ascii')
+        sr = codecs.StreamRecoder(bio, codec.encode, codec.decode,
+                                  encodings.ascii.StreamReader, encodings.ascii.StreamWriter)
+        sr.writelines([b'a', b'b'])
+        self.assertEqual(bio.getvalue(), b'ab')
+
+    def test_write(self):
+        bio = io.BytesIO()
+        codec = codecs.lookup('latin1')
+        # Recode from Latin-1 to utf-8.
+        sr = codecs.StreamRecoder(bio, codec.encode, codec.decode,
+                                  encodings.utf_8.StreamReader, encodings.utf_8.StreamWriter)
+
+        text = 'àñé'
+        sr.write(text.encode('latin1'))
+        self.assertEqual(bio.getvalue(), text.encode('utf-8'))
+
+
 @unittest.skipIf(_testcapi is None, 'need _testcapi module')
 class LocaleCodecTest(unittest.TestCase):
     """
diff --git a/Misc/NEWS.d/next/Documentation/2018-05-13-10-36-37.bpo-33482.jalAaQ.rst b/Misc/NEWS.d/next/Documentation/2018-05-13-10-36-37.bpo-33482.jalAaQ.rst
new file mode 100644
index 00000000000000..bda5be87723d45
--- /dev/null
+++ b/Misc/NEWS.d/next/Documentation/2018-05-13-10-36-37.bpo-33482.jalAaQ.rst
@@ -0,0 +1 @@
+Make `codecs.StreamRecoder.writelines` take a list of bytes.