diff --git a/app/models/foreman_fog_proxmox/proxmox_interfaces.rb b/app/models/foreman_fog_proxmox/proxmox_interfaces.rb
index 9d98125a5..7f5a1a665 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)
+      nic_compute_attributes[mac_key] = Net::Validations.normalize_mac(mac).upcase
     end
 
     def host_interfaces_attrs(host)
diff --git a/test/unit/foreman_fog_proxmox/proxmox_interfaces_test.rb b/test/unit/foreman_fog_proxmox/proxmox_interfaces_test.rb
index 7e4365a88..0115eff2c 100644
--- a/test/unit/foreman_fog_proxmox/proxmox_interfaces_test.rb
+++ b/test/unit/foreman_fog_proxmox/proxmox_interfaces_test.rb
@@ -54,7 +54,7 @@ class ProxmoxInterfacesTest < ActiveSupport::TestCase
 
       it 'sets interface identifier with server compute id, ip and ip6 and mac adress' do
         ip = '192.168.56.100'
-        mac_address = '36:25:8c:53:0c:50'
+        mac_address = '36:25:8C:53:0C:50'
         ip6 = Array.new(4) { format('%<x>s', x: rand(16**4)) }.join(':') + '::1'
         compute_attributes = ActiveSupport::HashWithIndifferentAccess.new({ 'id' => 'net0' })
         physical_nic = FactoryBot.build(:nic_base_empty, :identifier => 'net0', :ip => ip, :ip6 => ip6,
@@ -131,7 +131,7 @@ class ProxmoxInterfacesTest < ActiveSupport::TestCase
 
       it 'sets container compute ip DHCP, mac adress and firewall' do
         ip = '192.168.56.100'
-        mac_address = '36:25:8c:53:0c:50'
+        mac_address = '36:25:8C:53:0C:50'
         ip6 = '2001:0:1234::c1c0:abcd:876'
         firewall = '1'
         compute_attributes = ActiveSupport::HashWithIndifferentAccess.new({ 'id' => 'net0', 'dhcp' => '1',