diff --git a/keystoneclient/v3/roles.py b/keystoneclient/v3/roles.py
index 8908e227a..022a4ecf5 100644
--- a/keystoneclient/v3/roles.py
+++ b/keystoneclient/v3/roles.py
@@ -57,14 +57,20 @@ class RoleManager(base.CrudManager):
         return base_url % params
 
     def _require_domain_xor_project(self, domain, project):
-        if (domain and project) or (not domain and not project):
+        if domain and project:
             msg = 'Specify either a domain or project, not both'
             raise exceptions.ValidationError(msg)
+        elif not (domain or project):
+            msg = 'Must specify either a domain or project'
+            raise exceptions.ValidationError(msg)
 
     def _require_user_xor_group(self, user, group):
-        if (user and group) or (not user and not group):
+        if user and group:
             msg = 'Specify either a user or group, not both'
             raise exceptions.ValidationError(msg)
+        elif not (user or group):
+            msg = 'Must specify either a user or group'
+            raise exceptions.ValidationError(msg)
 
     def create(self, name):
         return super(RoleManager, self).create(