diff --git a/openbook_auth/tests/views/test_auth.py b/openbook_auth/tests/views/test_auth.py
index 6cc3a937..d30eea17 100644
--- a/openbook_auth/tests/views/test_auth.py
+++ b/openbook_auth/tests/views/test_auth.py
@@ -96,7 +96,7 @@ def test_invalid_username(self):
         should return 400 if the username is not valid
         """
         url = self._get_url()
-        invalid_usernames = ('joel<;<', '<>', ' shantanu space ', 'greater_than_30_characters_username_is_not_valid',)
+        invalid_usernames = ('joel<;<', '<>', ' shantanu space ', 'greater_than_30_characters_username_is_not_valid','.start_with_period','more_than__one_special_char','end_with_period.')
         token = self._make_user_invite_token()
         for username in invalid_usernames:
             data = {
diff --git a/openbook_auth/validators.py b/openbook_auth/validators.py
index 5ac1e3fa..d77ee56b 100644
--- a/openbook_auth/validators.py
+++ b/openbook_auth/validators.py
@@ -6,9 +6,11 @@
 
 
 def username_characters_validator(username):
-    if not re.match('^[a-zA-Z0-9_.]*$', username):
+    if not re.match("^[a-zA-Z0-9](?:[._]?[a-z-A-Z0-9])*$", username):
         raise ValidationError(
-            _('Usernames can only contain alphanumeric characters, periods and underscores.'),
+            _(
+                'Usernames can only contain alphanumeric characters, periods and underscores. They must not begin or end with a period or underscore.'
+        )
         )