diff --git a/Library/Homebrew/os/mac.rb b/Library/Homebrew/os/mac.rb
index 7fa95cd560b63b3b51efa6884e733b092b9f01af..c4437f0fd54e269d10f1f8d0a4755e3b9eac2635 100644
--- a/Library/Homebrew/os/mac.rb
+++ b/Library/Homebrew/os/mac.rb
@@ -282,7 +282,7 @@ module OS
     end
 
     def pkgutil_info(id)
-      (@pkginfo ||= {}).fetch(id.to_s) do |key|
+      (@pkginfo ||= {}).fetch(id) do |key|
         @pkginfo[key] = `/usr/sbin/pkgutil --pkg-info "#{key}" 2>/dev/null`.strip
       end
     end