diff --git a/c2corg_api/tests/views/test_user.py b/c2corg_api/tests/views/test_user.py
index 8f8811808..77d4861d4 100644
--- a/c2corg_api/tests/views/test_user.py
+++ b/c2corg_api/tests/views/test_user.py
@@ -196,6 +196,35 @@ def test_register_forum_username_unique(self, _send_email):
         self.assertEqual(json['errors'][0]['description'],
                          'already used forum_username')
 
+    @patch('c2corg_api.emails.email_service.EmailService._send_email')
+    def test_register_stripped_username(self, _send_email):
+        request_body = {
+            'username': ' contributor ',
+            'forum_username': 'Foo',
+            'name': 'Max Mustermann',
+            'password': 'super secret',
+            'email': 'some_user@camptocamp.org'
+        }
+        url = self._prefix + '/register'
+        json = self.app_post_json(url, request_body, status=400).json
+        self.assertEqual(json['errors'][0]['description'],
+                         'This username already exists')
+
+        request_body = {
+            'username': ' username with spaces ',
+            'forum_username': 'Spaceman',
+            'name': 'Max Mustermann',
+            'password': 'super secret',
+            'email': 'space@camptocamp.org'
+        }
+        url = self._prefix + '/register'
+        body = self.app_post_json(url, request_body, status=200).json
+        self.assertBodyEqual(body, 'username', 'username with spaces')
+        user_id = body.get('id')
+        user = self.session.query(User).get(user_id)
+        self.assertIsNotNone(user)
+        self.assertEqual(user.username, 'username with spaces')
+
     @patch('c2corg_api.emails.email_service.EmailService._send_email')
     def test_register_username_email_not_equals_email(self, _send_email):
         request_body = {
diff --git a/c2corg_api/views/user.py b/c2corg_api/views/user.py
index 3f569fe66..9f5c9c303 100644
--- a/c2corg_api/views/user.py
+++ b/c2corg_api/views/user.py
@@ -123,21 +123,36 @@ def validate_forum_username(request, **kwargs):
 
 
 def validate_username(request, **kwargs):
+    """Checks username is set, strips leading/trailing whitespaces,
+       checks unicity and if an email, that it matches the provided email.
     """
-    Check that the username is not an email,
-    or that it is the same as the actual email.
-    """
-    if 'username' in request.json and 'email' in request.json:
-        value = request.json['username']
+
+    if 'username' not in request.json:
+        request.errors.add('body', 'username', 'Required')
+        return
+
+    username = request.json['username'].strip()
+    if not username:
+        request.errors.add('body', 'username',
+                           'Username cannot be empty or whitespaces')
+        return
+
+    if not is_unused_user_attribute('username', username, lowercase=True):
+        request.errors.add('body', 'username', 'This username already exists')
+
+    # Check that the username is not an email,
+    # or that it is the same as the actual email.
+    if 'email' in request.json:
         email = request.json['email']
-        if (is_valid_email(value) and email != value):
+        if (is_valid_email(username) and email != username):
             request.errors.add(
                 'body',
                 'username',
                 'An email address used as username should be the same as the' +
                 ' one used as the account email address.')
             return
-        request.validated['username'] = value
+
+    request.validated['username'] = username
 
 
 def validate_captcha(request, **kwargs):
@@ -189,7 +204,6 @@ def __init__(self, request):
             colander_body_validator,
             validate_json_password,
             partial(validate_unique_attribute, "email"),
-            partial(validate_unique_attribute, "username"),
             partial(validate_unique_attribute,
                     "forum_username",
                     lowercase=True),