diff --git a/docs/api_generic.rst b/docs/api_generic.rst
index 621154f..ce047c9 100644
--- a/docs/api_generic.rst
+++ b/docs/api_generic.rst
@@ -87,6 +87,9 @@ Base Classes
 .. autoclass:: CompositeDevice(\*args, _order=None, \*\*kwargs)
     :members:
 
+.. autoclass:: CompositeOutputDevice(\*args, _order=None, \*\*kwargs)
+    :members:
+
 Input Devices
 =============
 
@@ -114,18 +117,12 @@ Output Devices
 SPI Devices
 ===========
 
-.. autoclass:: SPIDevice
-    :members:
-
 .. autoclass:: AnalogInputDevice
     :members:
 
 Composite Devices
 =================
 
-.. autoclass:: CompositeOutputDevice
-    :members:
-
 .. autoclass:: LEDCollection
     :members:
 
diff --git a/gpiozero/boards.py b/gpiozero/boards.py
index 689492a..11c8122 100644
--- a/gpiozero/boards.py
+++ b/gpiozero/boards.py
@@ -31,6 +31,13 @@ class CompositeOutputDevice(SourceMixin, CompositeDevice):
     Extends :class:`CompositeDevice` with :meth:`on`, :meth:`off`, and
     :meth:`toggle` methods for controlling subordinate output devices.  Also
     extends :attr:`value` to be writeable.
+
+    :param list _order:
+        If specified, this is the order of named items specified by keyword
+        arguments (to ensure that the :attr:`value` tuple is constructed with a
+        specific order). All keyword arguments *must* be included in the
+        collection. If omitted, an alphabetically sorted order will be selected
+        for keyword arguments.
     """
 
     def on(self):
diff --git a/gpiozero/devices.py b/gpiozero/devices.py
index c89ae17..3f256df 100644
--- a/gpiozero/devices.py
+++ b/gpiozero/devices.py
@@ -257,8 +257,8 @@ class CompositeDevice(Device):
         If specified, this is the order of named items specified by keyword
         arguments (to ensure that the :attr:`value` tuple is constructed with a
         specific order). All keyword arguments *must* be included in the
-        collection. If omitted, an arbitrary order will be selected for keyword
-        arguments.
+        collection. If omitted, an alphabetically sorted order will be selected
+        for keyword arguments.
     """
     def __init__(self, *args, **kwargs):
         self._all = ()