diff --git a/ckan/logic/action/create.py b/ckan/logic/action/create.py
index 0d7a5c220c2..1a124f4eb85 100644
--- a/ckan/logic/action/create.py
+++ b/ckan/logic/action/create.py
@@ -1106,7 +1106,7 @@ def user_invite(context, data_dict):
 
 def _get_random_username_from_email(email):
     localpart = email.split('@')[0]
-    cleaned_localpart = re.sub(r'[^\w]', '-', localpart)
+    cleaned_localpart = re.sub(r'[^\w]', '-', localpart).lower()
 
     # if we can't create a unique user name within this many attempts
     # then something else is probably wrong and we should give up
diff --git a/ckan/tests/logic/action/test_create.py b/ckan/tests/logic/action/test_create.py
index 78fbf287f67..57c7b8e2309 100644
--- a/ckan/tests/logic/action/test_create.py
+++ b/ckan/tests/logic/action/test_create.py
@@ -75,6 +75,12 @@ def test_requires_role(self, _):
     def test_requires_group_id(self, _):
         self._invite_user_to_group(group={'id': None})
 
+    @mock.patch('ckan.lib.mailer.send_invite')
+    def test_user_name_lowercase_when_email_is_uppercase(self, _):
+        invited_user = self._invite_user_to_group(email='Maria@example.com')
+
+        assert_equals(invited_user.name.split('-')[0], 'maria')
+
     def _invite_user_to_group(self, email='user@email.com',
                               group=None, role='member'):
         user = factories.User()