diff --git a/aodh/api/controllers/v2/alarm_rules/composite.py b/aodh/api/controllers/v2/alarm_rules/composite.py
index 33c8af173..5062a899a 100644
--- a/aodh/api/controllers/v2/alarm_rules/composite.py
+++ b/aodh/api/controllers/v2/alarm_rules/composite.py
@@ -52,7 +52,7 @@ class CompositeRule(wtypes.UserType):
     @staticmethod
     def valid_composite_rule(rules):
         if isinstance(rules, dict) and len(rules) == 1:
-            and_or_key = rules.keys()[0]
+            and_or_key = list(rules)[0]
             if and_or_key not in ('and', 'or'):
                 raise base.ClientSideError(
                     _('Threshold rules should be combined with "and" or "or"'))