diff --git a/openwisp_controller/config/controller/views.py b/openwisp_controller/config/controller/views.py
index dfbcc40ec..2e51964ec 100644
--- a/openwisp_controller/config/controller/views.py
+++ b/openwisp_controller/config/controller/views.py
@@ -287,7 +287,10 @@ def init_object(self, **kwargs):
                 device_model._meta.get_field(attr)
             except FieldDoesNotExist:
                 continue
-            options[attr] = kwargs.get(attr)
+            if attr == 'mac_address':
+                options[attr] = kwargs.get(attr).upper()
+            else:
+                options[attr] = kwargs.get(attr)
         # do not specify key if:
         #   app_settings.CONSISTENT_REGISTRATION is False
         #   if key is ``None`` (it would cause exception)