diff --git a/web/channels/room_channel.ex b/web/channels/room_channel.ex
index 6f20780..f590455 100644
--- a/web/channels/room_channel.ex
+++ b/web/channels/room_channel.ex
@@ -1,12 +1,14 @@
 defmodule KolabChat.RoomChannel do
   use KolabChat.Web, :channel
 
+  @spec join(topic :: binary(), args :: map(), socket :: pid()) :: {:ok, socket :: pid()}
   def join("room:lobby", _, socket) do
     {:ok, socket}
   end
 
+  @spec handle_in(topic :: binary, args :: map(), socket :: pid()) :: {:noreply, socket :: pid()}
   def handle_in("new:message", message, socket) do
     broadcast! socket, "new:message", %{user: message["user"], body: message["body"]}
     {:noreply, socket}
   end
 end
diff --git a/web/channels/system_channel.ex b/web/channels/system_channel.ex
index a520a46..6011fd7 100644
--- a/web/channels/system_channel.ex
+++ b/web/channels/system_channel.ex
@@ -1,105 +1,108 @@
 defmodule KolabChat.SystemChannel do
   use KolabChat.Web, :channel
 
   @status [
     # user is available for chat
     :online,
     :away,
     # user is connected and visible, but not available
     :busy,
     :unavailable,
     # user is shown as offline
     :invisible,
     :offline
   ]
 
+  @spec join(topic :: binary(), args :: map(), socket :: pid()) :: {:ok, socket :: pid()}
   def join("system", %{"context" => context}, socket) do
     perform_join(context, socket)
   end
 
   def join("system", _args, socket) do
     perform_join("default", socket)
   end
 
+  @spec handle_info(:after_join, socket :: pid()) :: {:noreply, socket :: pid()}
   def handle_info(:after_join, socket) do
     push socket, "presence_state", Presence.list(socket)
     push socket, "info", %{user: socket.assigns.user.username}
 
     Presence.track(socket, socket.assigns.user.username, %{
       status: get_user_status(socket),
       context: socket.assigns.context
     })
 
     {:noreply, socket}
   end
 
+  @spec handle_in(topic :: binary, args :: map(), socket :: pid()) :: {:noreply, socket :: pid()}
   def handle_in("set-status", %{"status" => status}, socket) do
     status = check_status(status)
     socket
       |> update_presence_status(status)
       |> set_user_status(status)
 
     {:noreply, socket}
   end
 
   defp perform_join(context, socket) do
     socket = assign(socket, :context, context)
     send self(), :after_join
 
     {:ok, socket}
   end
 
   defp update_presence_status(socket, :invalid), do: socket
   defp update_presence_status(socket, status) do
     Presence.update(socket, socket.assigns.user.username, %{
       status: status,
       context: socket.assigns.context
     })
 
     socket
   end
 
   # Makes sure the provided status name is supported
   # Returns status name as an atom
   defp check_status(status) do
     status = String.to_atom(status)
 
     if Enum.member?(@status, status) do
       status
     else
       :invalid
     end
   end
 
   # Get the last user/context status from the database
   defp get_user_status(socket) do
     require Amnesia
     require Amnesia.Helper
 
     key = socket.assigns.user.username <> ":" <> socket.assigns.context
 
     Amnesia.transaction do
       case Database.Status.read(key) do
         # use last status
         %Database.Status{status: status} -> status
         # otherwise set status to online
         _ -> :online
       end
     end
   end
 
   # Save the current user/context status to the database
   defp set_user_status(socket, :invalid), do: socket
   defp set_user_status(socket, status) do
     require Amnesia
     require Amnesia.Helper
 
     key = socket.assigns.user.username <> ":" <> socket.assigns.context
 
     Amnesia.transaction do
       Database.Status.write(%Database.Status{key: key, status: status})
     end
 
     socket
   end
 end