diff --git a/lib/jekyll/reader.rb b/lib/jekyll/reader.rb
index da2d1e1d..99aa746c 100644
--- a/lib/jekyll/reader.rb
+++ b/lib/jekyll/reader.rb
@@ -63,8 +63,8 @@ module Jekyll
     # Returns nothing.
     def retrieve_posts(dir)
       return if outside_configured_directory?(dir)
-      site.posts.docs.concat(PostReader.new(site).read_posts(dir))
-      site.posts.docs.concat(PostReader.new(site).read_drafts(dir)) if site.show_drafts
+      site.posts.docs.concat(post_reader.read_posts(dir))
+      site.posts.docs.concat(post_reader.read_drafts(dir)) if site.show_drafts
     end
 
     # Recursively traverse directories with the read_directories function.
@@ -146,5 +146,11 @@ module Jekyll
       collections_dir = site.config["collections_dir"]
       !collections_dir.empty? && !dir.start_with?("/#{collections_dir}")
     end
+
+    # Create a single PostReader instance to retrieve drafts and posts from all valid
+    # directories in current site.
+    def post_reader
+      @post_reader ||= PostReader.new(site)
+    end
   end
 end