diff --git a/patrole_tempest_plugin/policy_authority.py b/patrole_tempest_plugin/policy_authority.py
index 3339a5d..bd1830f 100644
--- a/patrole_tempest_plugin/policy_authority.py
+++ b/patrole_tempest_plugin/policy_authority.py
@@ -99,7 +99,7 @@
             # "service:another_test_rule", which means that the default policy
             # rule is used: "rule:admin_or_owner".
         """
-
+        service = service.lower()
         if extra_target_data is None:
             extra_target_data = {}
 
@@ -145,13 +145,13 @@
         ``cls.available_services``. Pick the first candidate path found
         out of the potential paths in ``[patrole] custom_policy_files``.
         """
-        if not hasattr(cls, 'policy_files'):
+        p_files = getattr(cls, 'policy_files', None)
+        if not p_files:
             cls.policy_files = {}
             for service in cls.available_services:
                 for candidate_path in CONF.patrole.custom_policy_files:
-                    if os.path.isfile(candidate_path % service):
-                        cls.policy_files.setdefault(service,
-                                                    candidate_path % service)
+                    if service in candidate_path.lower() and os.path.isfile(candidate_path):
+                        cls.policy_files.setdefault(service, candidate_path)
 
     def allowed(self, rule_name, role):
         """Checks if a given rule in a policy is allowed with given role.