diff --git a/db/migrate/20130221215017_add_description_to_categories.rb b/db/migrate/20130221215017_add_description_to_categories.rb
index aa225680146..24514a4720a 100644
--- a/db/migrate/20130221215017_add_description_to_categories.rb
+++ b/db/migrate/20130221215017_add_description_to_categories.rb
@@ -8,10 +8,20 @@ class AddDescriptionToCategories < ActiveRecord::Migration[4.2]
     remove_column :categories, :top1_user_id
     remove_column :categories, :top2_user_id
 
-    # Migrate excerpts over
-    Category.order('id').each do |c|
-      post = c.topic.posts.order(:post_number).first
-      PostRevisor.new(post).send(:update_category_description)
+    # some ancient installs may have bad category descriptions
+    # attempt to fix
+    if !DB.query_single("SELECT 1 FROM categories limit 1").empty?
+
+      # Reaching into post revisor is not ideal here, but this code
+      # should almost never run, so bypass it
+      Discourse.reset_active_record_cache
+
+      Category.order('id').each do |c|
+        post = c.topic.ordered_posts.first
+        PostRevisor.new(post).update_category_description
+      end
+
+      Discourse.reset_active_record_cache
     end
 
   end