diff --git a/src/transport/efka_heartbeat.erl b/src/transport/efka_heartbeat.erl
index 21b103d..77b16bc 100644
--- a/src/transport/efka_heartbeat.erl
+++ b/src/transport/efka_heartbeat.erl
@@ -100,7 +100,7 @@ code_change(_OldVsn, State, _Extra) ->
 
 -spec send_heartbeat(#state{}) -> ok.
 send_heartbeat(#state{socket = Socket, host = Host, port = Port, uuid = UUID, heartbeat_secret = HeartbeatSecret}) ->
-    Packet = heartbeat_packet(UUID, HeartbeatSecret),
+    Packet = heartbeat_packet_iodata(UUID, HeartbeatSecret),
     case gen_udp:send(Socket, Host, Port, Packet) of
         ok ->
             ok;
@@ -109,11 +109,11 @@ send_heartbeat(#state{socket = Socket, host = Host, port = Port, uuid = UUID, he
             ok
     end.
 
--spec heartbeat_packet(binary(), binary()) -> binary().
-heartbeat_packet(UUID, HeartbeatSecret) when is_binary(UUID), is_binary(HeartbeatSecret) ->
+-spec heartbeat_packet_iodata(binary(), binary()) -> iodata().
+heartbeat_packet_iodata(UUID, HeartbeatSecret) when is_binary(UUID), is_binary(HeartbeatSecret) ->
     UUIDLen = byte_size(UUID),
     Timestamp = efka_util:timestamp(),
     Nonce = crypto:strong_rand_bytes(?HEARTBEAT_NONCE_BYTES),
     Payload = <<?HEARTBEAT_VERSION:8, UUIDLen:16, UUID:UUIDLen/binary, Timestamp:64/unsigned-big, Nonce/binary>>,
     Mac = crypto:mac(hmac, sha256, HeartbeatSecret, Payload),
-    <<Payload/binary, Mac/binary>>.
+    [Payload, Mac].