diff --git a/build/owncloud/rainloop-app/css/style.css b/build/owncloud/rainloop-app/css/style.css
new file mode 100644
index 000000000..462226253
--- /dev/null
+++ b/build/owncloud/rainloop-app/css/style.css
@@ -0,0 +1,6 @@
+/*
+Empty style sheet!
+Only needed to give you the opportunity to theme the owncloud part
+of the rainloop app with the theming system integrated in ownCoud
+if the rainloop app is activated.
+*/
\ No newline at end of file
diff --git a/build/owncloud/rainloop-app/index.php b/build/owncloud/rainloop-app/index.php
index 30bbb4f5d..931ecf153 100644
--- a/build/owncloud/rainloop-app/index.php
+++ b/build/owncloud/rainloop-app/index.php
@@ -13,6 +13,10 @@ OCP\User::checkLoggedIn();
 OCP\App::checkAppEnabled('rainloop');
 OCP\App::setActiveNavigationEntry('rainloop_index');
 
+// Load the empty file ../css/style.css, that's needed to allow theming of
+// the ownCloud header and navigation if rainloop is the active app.
+OCP\Util::addStyle('rainloop', 'style');
+
 include_once OC_App::getAppPath('rainloop').'/lib/RainLoopHelper.php';
 
 $sUrl = OC_RainLoop_Helper::normalizeUrl(OC_RainLoop_Helper::getAppUrl());