diff --git a/lib/jekyll/post.rb b/lib/jekyll/post.rb
index e570baaf..c227e318 100644
--- a/lib/jekyll/post.rb
+++ b/lib/jekyll/post.rb
@@ -96,6 +96,7 @@ module Jekyll
     #
     # Returns [<Post>]
     def related_posts(posts)
+      return [] unless posts.size > 1
       self.class.lsi ||= begin
         puts "Running the classifier... this could take a while."
         lsi = Classifier::LSI.new
@@ -145,4 +146,4 @@ module Jekyll
     end
   end
 
-end
\ No newline at end of file
+end