diff --git a/_modules/maas.py b/_modules/maas.py
index 3c6fce9..0152eba 100644
--- a/_modules/maas.py
+++ b/_modules/maas.py
@@ -548,10 +548,10 @@
     def _get_nic_id_by_mac(self, machine, req_mac=None):
         data = {}
         for nic in machine['interface_set']:
-            data[nic['mac_address']] = nic['id']
+            data[nic['mac_address'].lower()] = nic['id']
         if req_mac:
-            if req_mac in data.keys():
-                return data[req_mac]
+            if req_mac.lower() in data.keys():
+                return data[req_mac.lower()]
             else:
                 raise Exception('NIC with mac:{} not found at '
                                 'node:{}'.format(req_mac, machine['fqdn']))