This looks like a typo.

Author: Morgan Haskel

lib/puppet/provider/firewall/ip6tables.rb

@@ -36,7 +36,7 @@
 
   confine :kernel => :linux
 
-  ip6tables_version = Facter.fact('iptables_version').value
+  ip6tables_version = Facter.fact('ip6tables_version').value
   if (ip6tables_version and Puppet::Util::Package.versioncmp(ip6tables_version, '1.4.1') < 0)
     mark_flag = '--set-mark'
   else