diff --git a/lib/jekyll-pandoc-multiple-formats/generator.rb b/lib/jekyll-pandoc-multiple-formats/generator.rb
index 5a57b2c..a8174ea 100644
--- a/lib/jekyll-pandoc-multiple-formats/generator.rb
+++ b/lib/jekyll-pandoc-multiple-formats/generator.rb
@@ -50,6 +50,13 @@ def generate(site)
       @site.post_attr_hash('categories').each_pair do |title, posts|
         posts.sort!
         pandoc_file = PandocFile.new(@site, output, posts, title)
+
+        if @site.keep_files.include? pandoc_file.relative_path
+          puts "#{pandoc_file.relative_path} is a category file AND a post file"
+          puts 'change the category name to fix this'
+          next
+        end
+
         next unless pandoc_file.write
 
         @site.keep_files << pandoc_file.relative_path
diff --git a/lib/jekyll-pandoc-multiple-formats/pandoc_file.rb b/lib/jekyll-pandoc-multiple-formats/pandoc_file.rb
index a145c20..14b698f 100644
--- a/lib/jekyll-pandoc-multiple-formats/pandoc_file.rb
+++ b/lib/jekyll-pandoc-multiple-formats/pandoc_file.rb
@@ -41,12 +41,12 @@ def initialize(site, format, posts, title = nil)
         raise ArgumentError.new "'title' argument is required for multipost file" unless title
 
         @title = title
-        @slug  = Utils.slugify(title)
       else
         @posts = [posts]
-        @slug  = posts.data['slug']
         @title = posts.data['title'] unless title
       end
+
+      @slug  = Utils.slugify(title)
     end
 
     def path