diff --git a/lib/gcm_on_rails/app/models/gcm/notification.rb b/lib/gcm_on_rails/app/models/gcm/notification.rb
index 8b144ac..2ea7adc 100644
--- a/lib/gcm_on_rails/app/models/gcm/notification.rb
+++ b/lib/gcm_on_rails/app/models/gcm/notification.rb
@@ -6,7 +6,7 @@ class Gcm::Notification < Gcm::Base
   serialize :data
 
   belongs_to :device, :class_name => 'Gcm::Device'
-  validates_presence_of :collapse_key if :time_to_live?
+  validates_presence_of :collapse_key, if: :time_to_live?
 
   class << self
     # Opens a connection to the Google GCM server and attempts to batch deliver