diff -r 07a6d4c30c4e Doc/library/functions.rst
--- a/Doc/library/functions.rst	Mon Dec 09 01:59:07 2013 +0100
+++ b/Doc/library/functions.rst	Mon Dec 09 16:55:59 2013 +0800
@@ -1178,8 +1178,10 @@
 .. function:: round(number[, ndigits])
 
    Return the floating point value *number* rounded to *ndigits* digits after
-   the decimal point.  If *ndigits* is omitted, it defaults to zero. Delegates
-   to ``number.__round__(ndigits)``.
+   the decimal point.  If *ndigits* is omitted, it defaults to zero. However,
+   while passing ``0`` to *ndigits* explicitely returns a float, omitting
+   *ndigits* returns an integer (so, for example, while ``round(1.2)`` is ``1``,
+   ``round(1.2, 0)`` is ``1.0``). Delegates to ``number.__round__(ndigits)``.
 
    For the built-in types supporting :func:`round`, values are rounded to the
    closest multiple of 10 to the power minus *ndigits*; if two multiples are