diff --git a/Library/Homebrew/cmd/audit.rb b/Library/Homebrew/cmd/audit.rb
index 2f3ffbc0be..0354210817 100755
--- a/Library/Homebrew/cmd/audit.rb
+++ b/Library/Homebrew/cmd/audit.rb
@@ -181,6 +181,7 @@ def audit_formula_urls f
   end
 
   urls = [(f.url rescue nil), (f.head rescue nil)].reject {|p| p.nil?}
+  urls.uniq! # head-only formulae result in duplicate entries
 
   f.mirrors.each do |m|
     mirror = m.values_at :url