diff --git a/apps/emqx_rule_engine/src/emqx_rule_engine_api.erl b/apps/emqx_rule_engine/src/emqx_rule_engine_api.erl
index 79be197aa..cb177630b 100644
--- a/apps/emqx_rule_engine/src/emqx_rule_engine_api.erl
+++ b/apps/emqx_rule_engine/src/emqx_rule_engine_api.erl
@@ -525,6 +525,10 @@ do_format_action(#{mod := Mod, func := Func, args := Args}) ->
     #{
         function => printable_function_name(Mod, Func),
         args => maps:remove(preprocessed_tmpl, Args)
+    };
+do_format_action(#{mod := Mod, func := Func}) ->
+    #{
+        function => printable_function_name(Mod, Func)
     }.
 
 printable_function_name(emqx_rule_actions, Func) ->