diff --git a/app/models/foreman_fog_proxmox/proxmox_interfaces.rb b/app/models/foreman_fog_proxmox/proxmox_interfaces.rb
index 7f5a1a665..9d98125a5 100644
--- a/app/models/foreman_fog_proxmox/proxmox_interfaces.rb
+++ b/app/models/foreman_fog_proxmox/proxmox_interfaces.rb
@@ -118,7 +118,7 @@ def dhcp?(nic_compute_attributes, v6 = false)
     def set_mac(nic_compute_attributes, mac, type)
       mac_attr_name = { 'qemu' => :macaddr, 'lxc' => :hwaddr }
       mac_key = mac_attr_name[type] || 'mac'
-      nic_compute_attributes[mac_key] = Net::Validations.normalize_mac(mac).upcase
+      nic_compute_attributes[mac_key] = Net::Validations.normalize_mac(mac)
     end
 
     def host_interfaces_attrs(host)