diff --git a/doc/config.rst b/doc/config.rst
index 5776dbb69..82ecdfdfd 100644
--- a/doc/config.rst
+++ b/doc/config.rst
@@ -40,6 +40,8 @@ Important points to note:
   delete them from the namespace with ``del`` if appropriate.  Modules are
   removed automatically, so you don't need to ``del`` your imports after use.
 
+.. _conf-tags:
+
 * There is a special object named ``tags`` available in the config file.
   It can be used to query and change the tags (see :ref:`tags`).  Use
   ``tags.has('tag')`` to query, ``tags.add('tag')`` and ``tags.remove('tag')``
diff --git a/doc/markup/misc.rst b/doc/markup/misc.rst
index 98ce5621b..b2e9051fd 100644
--- a/doc/markup/misc.rst
+++ b/doc/markup/misc.rst
@@ -176,8 +176,9 @@ Including content based on tags
       .. only:: html and draft
 
    Undefined tags are false, defined tags (via the ``-t`` command-line option or
-   within :file:`conf.py`) are true.  Boolean expressions, also using
-   parentheses (like ``html and (latex or draft)``) are supported.
+   within :file:`conf.py`, see :ref:`here <conf-tags>`) are true.  Boolean
+   expressions, also using parentheses (like ``html and (latex or draft)``) are
+   supported.
 
    The *format* and the *name* of the current builder (``html``, ``latex`` or
    ``text``) are always set as a tag [#]_.  To make the distinction between
@@ -185,6 +186,9 @@ Including content based on tags
    ``builder_``, e.g. the epub builder defines the tags  ``html``, ``epub``,
    ``format_html`` and ``builder_epub``.
 
+   These standard tags are set *after* the configuration file is read, so they
+   are not available there.
+
    .. versionadded:: 0.6
    .. versionchanged:: 1.2
       Added the name of the builder and the prefixes.