diff --git a/apps/iot/src/mocker/iot_mock.erl b/apps/iot/src/mocker/iot_mock.erl
index 77f2099..ee3a802 100644
--- a/apps/iot/src/mocker/iot_mock.erl
+++ b/apps/iot/src/mocker/iot_mock.erl
@@ -101,7 +101,7 @@ simple_mapper() ->
     Fields1 = lists:map(fun(#{<<\"key\">> := Key, <<\"value\">> := Val}) -> {Key, Val} end, Fields),
     Fields2 = maps:from_list(Fields1),
     Bin = jiffy:encode(Fields2#{<<\"location_code\">> => LocationCode}, [force_utf8]),
-    iolist_to_binary(Bin)
+    {ok, iolist_to_binary(Bin)}
       end.",
 
     Mapper = list_to_binary(Mapper0),
@@ -113,7 +113,7 @@ mysql_mapper() ->
     Mapper0 = "fun(LocationCode, Fields, Timestamp) ->
     Fields1 = lists:map(fun(#{<<\"key\">> := Key, <<\"value\">> := Val}) -> {Key, Val} end, Fields),
     Content = jiffy:encode(maps:from_list(Fields1), [force_utf8]),
-    [{<<\"location_code\">>, LocationCode}, {<<\"content\">>, Content}, {<<\"created_ts\">>, Timestamp}]
+    {ok, [{<<\"location_code\">>, LocationCode}, {<<\"content\">>, Content}, {<<\"created_ts\">>, Timestamp}]}
       end.",
 
     Mapper = list_to_binary(Mapper0),