diff --git a/Doc/library/decimal.rst b/Doc/library/decimal.rst
index 7052985..b491bcf 100644
--- a/Doc/library/decimal.rst
+++ b/Doc/library/decimal.rst
@@ -862,6 +862,14 @@ Decimal objects
       :const:`Rounded`.  If given, applies *rounding*; otherwise, uses the
       rounding method in either the supplied *context* or the current context.
 
+   .. method:: __format__(format)
+
+      Format as string using the given ``format``.
+
+      This makes it possible to specify format string for a :class:`Decimal`
+      object when using :meth:`str.format`. For a complete list of formatting
+      directives, see :ref:`formatspec`.
+
 
 .. _logical_operands_label:
 
diff --git a/Doc/library/string.rst b/Doc/library/string.rst
index f9da5fa..ca167c9 100644
--- a/Doc/library/string.rst
+++ b/Doc/library/string.rst
@@ -451,8 +451,9 @@ The available presentation types for floating point and decimal values are:
    |         | The precise rules are as follows: suppose that the       |
    |         | result formatted with presentation type ``'e'`` and      |
    |         | precision ``p-1`` would have exponent ``exp``.  Then     |
-   |         | if ``-4 <= exp < p``, the number is formatted            |
-   |         | with presentation type ``'f'`` and precision             |
+   |         | if ``m <= exp < p`` where ``m`` is -4 for floats and -6  |
+   |         | for :class:`Decimals <decimal.Decimal>`, the number is   |
+   |         | formatted with presentation type ``'f'`` and precision   |
    |         | ``p-1-exp``.  Otherwise, the number is formatted         |
    |         | with presentation type ``'e'`` and precision ``p-1``.    |
    |         | In both cases insignificant trailing zeros are removed   |