diff --git a/openwisp_controller/config/base/device.py b/openwisp_controller/config/base/device.py
index e3892a08b..e36e34d34 100644
--- a/openwisp_controller/config/base/device.py
+++ b/openwisp_controller/config/base/device.py
@@ -262,6 +262,7 @@ def _validate_unique_name(self):
 
     def clean(self, *args, **kwargs):
         super().clean(*args, **kwargs)
+        self.mac_address = self.mac_address.upper()
         self._validate_unique_name()
         self._validate_org_relation('group', field_error='group')
         self._validate_org_device_limit()
diff --git a/openwisp_controller/config/tests/test_device.py b/openwisp_controller/config/tests/test_device.py
index 462e59106..7768242a2 100644
--- a/openwisp_controller/config/tests/test_device.py
+++ b/openwisp_controller/config/tests/test_device.py
@@ -69,6 +69,14 @@ def test_mac_address_validator(self):
             else:
                 self.fail('ValidationError not raised for "{0}"'.format(mac_address))
 
+    def test_device_mac_address_uppercase(self):
+        device = self._create_device(mac_address='00:1a:2b:3c:4d:5e')
+        device.full_clean()
+        self.assertEqual(device.mac_address, '00:1A:2B:3C:4D:5E')
+        device.save()
+        device.refresh_from_db()
+        self.assertEqual(device.mac_address, '00:1A:2B:3C:4D:5E')
+
     def test_config_status_modified(self):
         c = self._create_config(device=self._create_device(), status='applied')
         self.assertEqual(c.status, 'applied')
diff --git a/openwisp_controller/geo/tests/test_api.py b/openwisp_controller/geo/tests/test_api.py
index ffc334ec2..9a9ba6c67 100644
--- a/openwisp_controller/geo/tests/test_api.py
+++ b/openwisp_controller/geo/tests/test_api.py
@@ -94,7 +94,7 @@ def test_put_create_location(self):
         device = self._create_object()
         self.assertEqual(self.location_model.objects.count(), 0)
         url = reverse(self.url_name, args=[device.pk])
-        r = self.client.put(f'{url}?key={device.key }')
+        r = self.client.put(f'{url}?key={device.key}')
         self.assertEqual(r.status_code, 200)
         self.assertDictEqual(
             r.json(),