diff --git a/documentation/ref-manual/tasks.rst b/documentation/ref-manual/tasks.rst
index 2e4b23408d..70c0dea3bb 100644
--- a/documentation/ref-manual/tasks.rst
+++ b/documentation/ref-manual/tasks.rst
@@ -412,12 +412,12 @@ them. You can learn more by looking at the
 -------------
 
 Unpacks the source code into a working directory pointed to by
-``${``\ :term:`WORKDIR`\ ``}``. The :term:`S`
-variable also plays a role in where unpacked source files ultimately
-reside. For more information on how source files are unpacked, see the
+``${``\ :term:`UNPACKDIR`\ ``}``. Another, legacy way to specify
+this directory is through the :term:`S` and :term:`WORKDIR` variables.
+For more information on how source files are unpacked, see the
 ":ref:`overview-manual/concepts:source fetching`"
 section in the Yocto Project Overview and Concepts Manual and also see
-the :term:`WORKDIR` and :term:`S` variable descriptions.
+the :term:`UNPACKDIR`, :term:`WORKDIR` and :term:`S` variable descriptions.
 
 Manually Called Tasks
 =====================
diff --git a/documentation/ref-manual/variables.rst b/documentation/ref-manual/variables.rst
index 546c674699..07b5b6f95c 100644
--- a/documentation/ref-manual/variables.rst
+++ b/documentation/ref-manual/variables.rst
@@ -9698,6 +9698,11 @@ system and gives an overview of their function and contents.
       :ref:`ref-classes-insane` class and is only enabled if the
       recipe inherits the :ref:`ref-classes-autotools` class.
 
+   :term:`UNPACKDIR`
+      This variable, used by the :ref:`ref-classes-base` class,
+      specifies where fetches sources should be unpacked by the
+      :ref:`ref-tasks-unpack` task.
+
    :term:`UPDATERCPN`
       For recipes inheriting the
       :ref:`ref-classes-update-rc.d` class, :term:`UPDATERCPN`