diff --git a/app/models/host.rb b/app/models/host.rb
index bfdce22..194dbd2 100644
--- a/app/models/host.rb
+++ b/app/models/host.rb
@@ -366,7 +366,7 @@ class Host < Puppet::Rails::Host
 
   def populateFieldsFromFacts
     unless SETTINGS[:ignore_puppet_facts_for_provisioning]
-      self.mac = fv(:macaddress).downcase
+      self.mac = fv(:macaddress).downcase if fv(:macaddress)
       self.ip = fv(:ipaddress) if ip.nil?
     end
     self.domain = Domain.find_or_create_by_name fv(:domain) unless fv(:domain).empty?