diff --git a/apps/emqx_rule_engine/include/rule_engine.hrl b/apps/emqx_rule_engine/include/rule_engine.hrl
index 9d01fefad..39c4daf69 100644
--- a/apps/emqx_rule_engine/include/rule_engine.hrl
+++ b/apps/emqx_rule_engine/include/rule_engine.hrl
@@ -60,7 +60,7 @@
         { id :: action_instance_id()
         , name :: action_name()
         , fallbacks :: list(#action_instance{})
-        , args :: #{atom() => term()} %% the args got from API for initializing action_instance
+        , args :: #{binary() => term()} %% the args got from API for initializing action_instance
         }).
 
 -record(rule,