diff -r 35b7dde7fd53 Doc/library/urllib.parse.rst
--- a/Doc/library/urllib.parse.rst	Fri Dec 12 13:19:48 2014 +0100
+++ b/Doc/library/urllib.parse.rst	Fri Dec 12 16:29:26 2014 +0100
@@ -537,8 +537,11 @@
    the value sequence for the key.  The order of parameters in the encoded
    string will match the order of parameter tuples in the sequence.
 
-   When *query* parameter is a :class:`str`, the *safe*, *encoding* and *error*
-   parameters are passed down to :func:`quote_plus` for encoding.
+   The *safe* parameter lists the ASCII characters that should not be percent-
+   encoded. Spaces are always replaced with the ``'+'`` character.
+
+   When *query* parameter is a :class:`str`, *encoding* and *error* parameters
+   are passed down to :func:`quote_plus` for encoding.
 
    To reverse this encoding process, :func:`parse_qs` and :func:`parse_qsl` are
    provided in this module to parse query strings into Python data structures.
diff -r 35b7dde7fd53 Lib/urllib/parse.py
--- a/Lib/urllib/parse.py	Fri Dec 12 13:19:48 2014 +0100
+++ b/Lib/urllib/parse.py	Fri Dec 12 16:29:26 2014 +0100
@@ -759,9 +759,11 @@
     parameters in the output will match the order of parameters in the
     input.
 
-    The components of a query arg may each be either a string or a bytes type.
-    When a component is a string, the safe, encoding and error parameters are
-    sent to the quote_plus function for encoding.
+    The safe arg may list ASCII characters or bytes that will not be encoded.
+
+    The components of the query arg may each be either str or bytes objects,
+    they will be encoded using the quote_plus function.  If a component is a
+    string, encoding and error parameters are sent to quote_plus for encoding.
     """
 
     if hasattr(query, "items"):