diff --git a/patrole_tempest_plugin/config.py b/patrole_tempest_plugin/config.py
index 5818843..df2a899 100644
--- a/patrole_tempest_plugin/config.py
+++ b/patrole_tempest_plugin/config.py
@@ -41,7 +41,7 @@
 assumes Patrole is on the same host as the policy files. The paths should be
 ordered by precedence, with high-priority paths before low-priority paths. All
 the paths that are found to contain the service's policy file will be used and
-all policy files will be merged.
+all policy files will be merged. Allowed ``json`` or ``yaml`` formats.
 """),
     cfg.BoolOpt('test_custom_requirements',
                 default=False,