diff --git a/apps/iot/src/endpoint/iot_jinzhi_endpoint.erl b/apps/iot/src/endpoint/iot_jinzhi_endpoint.erl
index 14c89c9..0299f11 100644
--- a/apps/iot/src/endpoint/iot_jinzhi_endpoint.erl
+++ b/apps/iot/src/endpoint/iot_jinzhi_endpoint.erl
@@ -196,7 +196,8 @@ format_event(LocationCode, DynamicLocationCode, EventType, #{<<"event_code">> :=
                         true ->
                             Len = length(FakeLocationCodes),
                             RandomIndex = rand:uniform(Len),
-                            lists:nth(RandomIndex, FakeLocationCodes);
+                            Code = lists:nth(RandomIndex, FakeLocationCodes),
+                            list_to_binary(Code);
                         false ->
                             LocationCode
                     end,