diff --git a/apps/efka/src/efka_transport.erl b/apps/efka/src/efka_transport.erl
index 33c62e3..eac520a 100644
--- a/apps/efka/src/efka_transport.erl
+++ b/apps/efka/src/efka_transport.erl
@@ -52,7 +52,9 @@ async_call_reply(undefined, PacketId, Response) when is_integer(PacketId), is_bi
 async_call_reply(Pid, PacketId, Response) when is_pid(Pid), is_integer(PacketId), is_binary(Response) ->
     gen_server:cast(Pid, {async_call_reply, PacketId, Response}).
 
--spec stop(Pid :: pid()) -> ok.
+-spec stop(Pid :: pid() | undefined) -> ok.
+stop(undefined) ->
+    ok;
 stop(Pid) when is_pid(Pid) ->
     gen_server:stop(Pid, normal, 2000).