diff --git a/Lib/codecs.py b/Lib/codecs.py
index a70ed20..3cd78fc 100644
--- a/Lib/codecs.py
+++ b/Lib/codecs.py
@@ -838,7 +838,7 @@
 
     def writelines(self, list):
 
-        data = ''.join(list)
+        data = b''.join(list)
         data, bytesdecoded = self.decode(data, self.errors)
         return self.writer.write(data)