diff --git a/app/models/user.rb b/app/models/user.rb
index f4f5d9f40fd..b350637af16 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -220,7 +220,8 @@ class User < ActiveRecord::Base
   end
 
   def saw_notification_id(notification_id)
-    User.where(["seen_notification_id < ?", notification_id]).update_all ["seen_notification_id = ?", notification_id]
+    User.where(["id = ? and seen_notification_id < ?", id, notification_id])
+        .update_all ["seen_notification_id = ?", notification_id]
   end
 
   def publish_notifications_state
diff --git a/db/migrate/20130809160751_fix_seen_notification_ids.rb b/db/migrate/20130809160751_fix_seen_notification_ids.rb
new file mode 100644
index 00000000000..9a83d826051
--- /dev/null
+++ b/db/migrate/20130809160751_fix_seen_notification_ids.rb
@@ -0,0 +1,14 @@
+class FixSeenNotificationIds < ActiveRecord::Migration
+  def up
+
+    # There was an error where `seen_notification_id` was being updated incorrectly.
+    # This tries to fix some of the bad data.
+    execute "UPDATE users SET
+              seen_notification_id = COALESCE((SELECT MAX(notifications.id)
+                                               FROM notifications
+                                               WHERE user_id = users.id AND created_at <= users.last_seen_at), 0)"
+  end
+
+  def down
+  end
+end