diff --git a/apps/iot/src/iot_env.erl b/apps/iot/src/iot_env.erl
index 8bf2711..24f95b6 100644
--- a/apps/iot/src/iot_env.erl
+++ b/apps/iot/src/iot_env.erl
@@ -46,7 +46,7 @@ get_value(Key, Default) when is_atom(Key) ->
             Val
     end.
 
--spec load_env() -> [binary()].
+-spec load_env() -> list().
 load_env() ->
     Dir = code:priv_dir(iot),
     EnvFile = Dir ++ "/env.config",