Error with ip6tables 'can't initialize ip6tables table `filter': Address family not supported by protocol'

Issue

• The following error is displayed when doing anything with ip6tables:

# ip6tables -L  
ip6tables v1.3.5: can't initialize ip6tables table `filter': Address family not supported by protocol  
Perhaps ip6tables or your kernel needs to be upgraded.  

# ip6tables --version  
ip6tables v1.3.5