diff --git a/apps/kolab_guam/src/kolab_guam_rule.erl b/apps/kolab_guam/src/kolab_guam_rule.erl
index 7578932..f82d1b7 100644
--- a/apps/kolab_guam/src/kolab_guam_rule.erl
+++ b/apps/kolab_guam/src/kolab_guam_rule.erl
@@ -1,26 +1,35 @@
 %% Copyright 2015 Kolab Systems AG (http://www.kolabsys.com)
 %%
 %% Aaron Seigo (Kolab Systems) <seigo a kolabsys.com>
 %%
 %% This program is free software: you can redistribute it and/or modify
 %% it under the terms of the GNU General Public License as published by
 %% the Free Software Foundation, either version 3 of the License, or
 %% (at your option) any later version.
 %%
 %% This program is distributed in the hope that it will be useful,
 %% but WITHOUT ANY WARRANTY; without even the implied warranty of
 %% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 %% GNU General Public License for more details.
 %%
 %% You should have received a copy of the GNU General Public License
 %% along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 -module(kolab_guam_rule).
 
--callback new(Args :: any()) -> any().
--callback applies(ConnectionDetails :: list(), Buffer :: binary(), SplitBinary :: { Tag :: binary(), Command :: binary(), Data :: binary() }, State :: any()) -> { true, State :: any() } |
-                                                                                      { false, State :: any() } |
-                                                                                      { notyet, State :: any() }.
--callback apply_to_client_message(ImapSession :: pid(), Command :: binary(), SplitBinary :: { Tag :: binary(), Command :: binary(), Data :: binary() }, State :: any()) -> { ProcessedCommand :: binary(), State :: any() }.
--callback apply_to_server_message(ImapSession :: pid(), Command :: binary(), State :: any()) -> { ProcessedCommand :: binary(), State :: any() }.
--callback imap_data(ResponseToken :: any(), Response :: any(), State :: any()) -> State ::any().
+-callback new(Args :: any()) ->
+    State :: any().
+
+-callback applies(ConnectionDetails :: list(), Buffer :: binary(), SplitBinary :: { Tag :: binary(), Command :: binary(), Data :: binary() }, State :: any()) ->
+    { true, State :: any() } |
+    { false, State :: any() } |
+    { notyet, State :: any() }.
+
+-callback apply_to_client_message(ImapSession :: pid(), Command :: binary(), SplitBinary :: { Tag :: binary(), Command :: binary(), Data :: binary() }, State :: any()) ->
+    { ProcessedCommand :: binary(), State :: any() }.
+
+-callback apply_to_server_message(ImapSession :: pid(), Command :: binary(), State :: any()) ->
+    { ProcessedCommand :: binary(), State :: any() }.
+
+-callback imap_data(ResponseToken :: any(), Response :: any(), State :: any()) ->
+    State :: any().