diff --git a/nova/policy.py b/nova/policy.py
index ad1b79c542..ea79e47b83 100644
--- a/nova/policy.py
+++ b/nova/policy.py
@@ -48,6 +48,22 @@ def reset():
         _ENFORCER = None


+def pick_file(policy_file):
+    if policy_file:
+        return policy file
+
+    if CONF.policy_file == DEFAULT_POLICY_FILE:
+        if os.path.exists(CONF.policy_file):
+            return CONF.policy_file
+        else:
+            # Do this smarter
+            json_backup = CONF.policy_file.replace('yaml', 'json')
+            if os.path.exists(json_backup):
+                return json_backup
+            # Same behavior if no overrides
+            return CONF.policy_file
+
+
 def init(policy_file=None, rules=None, default_rule=None, use_conf=True,
          suppress_deprecation_warnings=False):
     """Init an Enforcer class.
@@ -68,7 +84,7 @@ def init(policy_file=None, rules=None, default_rule=None, use_conf=True,

     if not _ENFORCER:
         _ENFORCER = policy.Enforcer(CONF,
-                                    policy_file=policy_file,
+                                    policy_file=pick_file(policy_file),
                                     rules=rules,
                                     default_rule=default_rule,
                                     use_conf=use_conf)