diff --git a/discord/client.py b/discord/client.py
index 4c06dcbf4..77b714669 100644
--- a/discord/client.py
+++ b/discord/client.py
@@ -88,9 +88,9 @@ class Client:
         Represents the current voice connection. None if you are not connected
         to a voice channel. To connect to voice use :meth:`join_voice_channel`.
         To query the voice connection state use :meth:`is_voice_connected`.
-    servers : list of :class:`Server`
+    servers : iterable of :class:`Server`
         The servers that the connected client is a member of.
-    private_channels : list of :class:`PrivateChannel`
+    private_channels : iterable of :class:`PrivateChannel`
         The private channels that the connected client is participating on.
     messages
         A deque_ of :class:`Message` that the client has received from all
diff --git a/discord/server.py b/discord/server.py
index 66ae3cd63..2d2afe6bc 100644
--- a/discord/server.py
+++ b/discord/server.py
@@ -67,9 +67,9 @@ class Server(Hashable):
     afk_channel : :class:`Channel`
         The channel that denotes the AFK channel. None if it doesn't exist.
     members
-        A list of :class:`Member` that are currently on the server.
+        An iterable of :class:`Member` that are currently on the server.
     channels
-        A list of :class:`Channel` that are currently on the server.
+        An iterable of :class:`Channel` that are currently on the server.
     icon : str
         The server's icon.
     id : str
diff --git a/docs/migrating.rst b/docs/migrating.rst
index 2cfa2bc62..c47986a20 100644
--- a/docs/migrating.rst
+++ b/docs/migrating.rst
@@ -122,6 +122,43 @@ After:
 In order for you to ``yield from`` or ``await`` a coroutine then your function must be decorated
 with ``@asyncio.coroutine`` or ``async def``.
 
+.. _migrating-iterable:
+
+Iterables
+----------
+
+For performance reasons, many of the internal data structures were changed into a dictionary to support faster
+lookup. As a consequence, this meant that some lists that were exposed via the API have changed into iterables
+and not sequences. In short, this means that certain attributes now only support iteration and not any of the
+sequence functions.
+
+The affected attributes are as follows:
+
+- :attr:`Client.servers`
+- :attr:`Client.private_channels`
+- :attr:`Server.channels`
+- :attr:`Server.members`
+
+Some examples of previously valid behaviour that is now invalid
+
+.. code-block:: python
+
+    if client.servers[0].name == "test":
+        # do something
+
+Since they are no longer ``list``\s, they no longer support indexing or any operation other than iterating.
+In order to get the old behaviour you should explicitly cast it to a list.
+
+.. code-block:: python
+
+    servers = list(client.servers)
+    # work with servers
+
+.. warning::
+
+    Due to internal changes of the structure, the order you receive the data in
+    is not in a guaranteed order.
+
 .. _migrating-enums:
 
 Enumerators