diff --git a/Library/Homebrew/extend/fileutils.rb b/Library/Homebrew/extend/fileutils.rb
index 9717c69f2e..b3e1da87fc 100644
--- a/Library/Homebrew/extend/fileutils.rb
+++ b/Library/Homebrew/extend/fileutils.rb
@@ -22,6 +22,8 @@ module FileUtils
     else
       Process.gid
     end
+    # Make OS X 10.6.7 (ruby-1.8.7-p174) and earlier happy.
+    group_id = group_id.to_s
     begin
       chown(nil, group_id, tmp)
     rescue Errno::EPERM