diff --git a/Casks/flowdock.rb b/Casks/flowdock.rb
index 8b23c3aa8..16e86d656 100644
--- a/Casks/flowdock.rb
+++ b/Casks/flowdock.rb
@@ -2,6 +2,7 @@ cask :v1 => 'flowdock' do
   version :latest
   sha256 :no_check
 
+  # amazonaws.com is the official download host per the vendor homepage
   url 'https://flowdock-resources.s3.amazonaws.com/mac/Flowdock.zip'
   appcast 'https://s3.amazonaws.com/flowdock-resources/mac/appcast.xml'
   homepage 'https://www.flowdock.com/'