diff --git a/Lib/codecs.py b/Lib/codecs.py
--- a/Lib/codecs.py
+++ b/Lib/codecs.py
@@ -863,20 +863,22 @@ def open(filename, mode='rb', encoding=N
     """ Open an encoded file using the given mode and return
         a wrapped version providing transparent encoding/decoding.
 
         Note: The wrapped version will only accept the object format
         defined by the codecs, i.e. Unicode objects for most builtin
         codecs. Output is also codec dependent and will usually be
         Unicode as well.
 
-        Files are always opened in binary mode, even if no binary mode
-        was specified. This is done to avoid data loss due to encodings
-        using 8-bit values. The default file mode is 'rb' meaning to
-        open the file in binary read mode.
+        If some encoding was specified, files will always be opened
+        in binary mode, even if no binary mode was specified. This is
+        done to avoid data loss due to encodings using 8-bit values.
+        If no encoding was specified, files will be opened with the
+        same mode as specified. The default file mode is 'rb' meaning
+        to open the file in binary read mode.
 
         encoding specifies the encoding which is to be used for the
         file.
 
         errors may be given to define the error handling. It defaults
         to 'strict' which causes ValueErrors to be raised in case an
         encoding error occurs.