diff --git a/Doc/library/io.rst b/Doc/library/io.rst
--- a/Doc/library/io.rst
+++ b/Doc/library/io.rst
@@ -754,7 +754,8 @@
    It inherits :class:`TextIOBase`.
 
    *encoding* gives the name of the encoding that the stream will be decoded or
-   encoded with.  It defaults to ``locale.getpreferredencoding(False)``.
+   encoded with.  It defaults to
+   :func:`locale.getpreferredencoding(False) <locale.getpreferredencoding>`.
 
    *errors* is an optional string that specifies how encoding and decoding
    errors are to be handled.  Pass ``'strict'`` to raise a :exc:`ValueError`
diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst
--- a/Doc/library/subprocess.rst
+++ b/Doc/library/subprocess.rst
@@ -238,10 +238,12 @@
    process should be captured into the same file handle as for *stdout*.
 
    When *stdout* or *stderr* are pipes and *universal_newlines* is
-   :const:`True` then the output data is assumed to be encoded as UTF-8 and
-   will automatically be decoded to text. All line endings will be converted
-   to ``'\n'`` as described for the universal newlines ``'U'`` mode argument
-   to :func:`open`.
+   ``True``, the output data will be decoded to text automatically
+   using the encoding returned by
+   :func:`locale.getpreferredencoding(False) <locale.getpreferredencoding>`.
+   All line endings will be converted to the system default using
+   universal newlines mode as described for the :class:`io.TextIOWrapper`
+   class when the *newline* argument to its constructor is ``None``.
 
    If *shell* is :const:`True`, the specified command will be executed through
    the shell. This can be useful if you are using Python primarily for the