diff --git a/lib/jekyll/site.rb b/lib/jekyll/site.rb
index b80e2226..eaba3d48 100644
--- a/lib/jekyll/site.rb
+++ b/lib/jekyll/site.rb
@@ -17,11 +17,14 @@ module Jekyll
       self.pygments        = config['pygments']
       self.permalink_style = config['permalink'].to_sym
 
+      self.reset
+      self.setup
+    end
+
+    def reset
       self.layouts         = {}
       self.posts           = []
       self.categories      = Hash.new { |hash, key| hash[key] = Array.new }
-
-      self.setup
     end
 
     def setup
@@ -85,6 +88,7 @@ module Jekyll
     #
     # Returns nothing
     def process
+      self.reset
       self.read_layouts
       self.transform_pages
       self.write_posts
diff --git a/test/test_site.rb b/test/test_site.rb
index e8d0ebb1..d3a2de04 100644
--- a/test/test_site.rb
+++ b/test/test_site.rb
@@ -9,6 +9,19 @@ class TestSite < Test::Unit::TestCase
       @site = Site.new(Jekyll.configuration)
     end
 
+    should "reset data before processing" do
+      clear_dest
+      @site.process
+      before_posts = @site.posts.length
+      before_layouts = @site.layouts.length
+      before_categories = @site.categories.length
+
+      @site.process
+      assert_equal before_posts, @site.posts.length
+      assert_equal before_layouts, @site.layouts.length
+      assert_equal before_categories, @site.categories.length
+    end
+
     should "read layouts" do
       @site.read_layouts
       assert_equal ["default", "simple"].sort, @site.layouts.keys.sort