diff --git a/lib/wayback_machine_downloader.rb b/lib/wayback_machine_downloader.rb
index bc71597..0e79623 100644
--- a/lib/wayback_machine_downloader.rb
+++ b/lib/wayback_machine_downloader.rb
@@ -135,8 +135,11 @@ class WaybackMachineDownloader
   end
 
   def list_files
+    # retrieval produces its own output
+    files = get_file_list_by_timestamp
+    # ... hence delay printing the opening bracket
     puts "["
-    get_file_list_by_timestamp.each do |file|
+    files.each do |file|
       puts file.to_json + ","
     end
     puts "]"