diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index b3a0a5f5192da1..2cc71a75af478e 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -47,7 +47,7 @@ Iterator            Arguments               Results
 ============================    ============================    =================================================   =============================================================
 Iterator                        Arguments                       Results                                             Example
 ============================    ============================    =================================================   =============================================================
-:func:`accumulate`              p [,func]                       p0, p0+p1, p0+p1+p2, ...                            ``accumulate([1,2,3,4,5]) --> 1 3 6 10 15``
+:func:`accumulate`              p [,func, \*, initial=None]     p0, p0+p1, p0+p1+p2, ...                            ``accumulate([1,2,3,4,5]) --> 1 3 6 10 15``
 :func:`chain`                   p, q, ...                       p0, p1, ... plast, q0, q1, ...                      ``chain('ABC', 'DEF') --> A B C D E F``
 :func:`chain.from_iterable`     iterable                        p0, p1, ... plast, q0, q1, ...                      ``chain.from_iterable(['ABC', 'DEF']) --> A B C D E F``
 :func:`compress`                data, selectors                 (d[0] if s[0]), (d[1] if s[1]), ...                 ``compress('ABCDEF', [1,0,1,0,1,1]) --> A C E F``
@@ -58,7 +58,7 @@ Iterator                        Arguments                       Results
 :func:`starmap`                 func, seq                       func(\*seq[0]), func(\*seq[1]), ...                 ``starmap(pow, [(2,5), (3,2), (10,3)]) --> 32 9 1000``
 :func:`takewhile`               pred, seq                       seq[0], seq[1], until pred fails                    ``takewhile(lambda x: x<5, [1,4,6,4,1]) --> 1 4``
 :func:`tee`                     it, n                           it1, it2, ... itn  splits one iterator into n
-:func:`zip_longest`             p, q, ...                       (p[0], q[0]), (p[1], q[1]), ...                     ``zip_longest('ABCD', 'xy', fillvalue='-') --> Ax By C- D-``
+:func:`zip_longest`             p, q, ... [, fillvalue=None]    (p[0], q[0]), (p[1], q[1]), ...                     ``zip_longest('ABCD', 'xy', fillvalue='-') --> Ax By C- D-``
 ============================    ============================    =================================================   =============================================================
 
 **Combinatoric iterators:**