diff -r 7bf3d91f8d6c Doc/tutorial/inputoutput.rst
--- a/Doc/tutorial/inputoutput.rst	Sun Jul 26 13:11:49 2015 +0200
+++ b/Doc/tutorial/inputoutput.rst	Tue Jul 28 20:04:10 2015 +0200
@@ -247,8 +247,9 @@
 omitted.
 
 Normally, files are opened in :dfn:`text mode`, that means, you read and write
-strings from and to the file, which are encoded in a specific encoding (the
-default being UTF-8).  ``'b'`` appended to the mode opens the file in
+strings from and to the file, which are encoded in a specific encoding (if
+encoding is not specified `the default is platform dependent <../library/functions.rst>`_.
+``'b'`` appended to the mode opens the file in
 :dfn:`binary mode`: now the data is read and written in the form of bytes
 objects.  This mode should be used for all files that don't contain text.
 
@@ -437,4 +438,3 @@
    written in other languages.  It is also insecure by default:
    deserializing pickle data coming from an untrusted source can execute
    arbitrary code, if the data was crafted by a skilled attacker.
-