diff --git a/src/m3ua_codec.erl b/src/m3ua_codec.erl
index 72876ea..03934c4 100644
--- a/src/m3ua_codec.erl
+++ b/src/m3ua_codec.erl
@@ -72,7 +72,7 @@
 encode_m3ua_msg(#m3ua_msg{version = Version, msg_class = MsgClass,
 			  msg_type = MsgType, payload = OptList}) ->
 	OptBin = encode_m3ua_opts(OptList),
-	MsgLen = length(OptBin) + 8,
+	MsgLen = byte_size(OptBin) + 8,
 	<<Version:4, 0:8, MsgClass:8, MsgType:8, MsgLen:32/big, OptBin/binary>>.
 
 encode_m3ua_opts(OptList) when is_list(OptList) ->
@@ -92,6 +92,6 @@
 		  payload = Payload} = Mtp3,
 	<<Opc:32/big, Dpc:32/big, Si:8, Ni:8, 0:8, Sls:8, Payload/binary>>;
 encode_m3ua_opt({Iei, Data}) when is_integer(Iei), is_binary(Data) ->
-	Length = length(Data) + 4,
+	Length = byte_size(Data) + 4,
 	PadLen = get_num_pad_bytes(Length),
 	<<Iei:16/big, Length:16/big, 0:PadLen/integer-unit:8, Data/binary>>.