diff --git a/scripts/generate_invoices.rb b/scripts/generate_invoices.rb
index 506bb8c..aa3fba7 100644
--- a/scripts/generate_invoices.rb
+++ b/scripts/generate_invoices.rb
@@ -60,6 +60,8 @@ members.each_with_index do |member, index|
   output_html_fn = File.join(output_dir, invoice.basename + '.html')
   output_pdf_fn = File.join(output_dir, invoice.basename + '.pdf')
 
+  next if File.exist?(output_html_fn)
+
   File.write(output_html_fn, result)
 
   system("wkhtmltopdf #{output_html_fn} #{output_pdf_fn}")