You want to enable the facts hash.
# if running a puppet version between 3.5 and 4.0
# in your puppet.conf file add -
[master]
# ... existing config ...
trusted_node_data = true
# and then restart your puppet master to apply the new setting
You will only need to explicitly enable the facts hash in puppet versions between 3.5 and 4.0. Earlier versions of Puppet do not support it and Puppet 4.0 and higher enable it by default.