diff --git a/Gemfile b/Gemfile
index fb3956c01..329ee0482 100644
--- a/Gemfile
+++ b/Gemfile
@@ -96,3 +96,6 @@ gem 'puma'
 
 # ical export
 gem 'icalendar'
+
+# removed from Rails 4.0
+gem 'rails-observers'