diff --git a/src/aeso_aci.erl b/src/aeso_aci.erl
index 767fcf7..1db0a01 100644
--- a/src/aeso_aci.erl
+++ b/src/aeso_aci.erl
@@ -135,7 +135,7 @@ encode_type(#tuple_t{args=As}) ->
     Eas = encode_types(As),
     [{<<"tuple">>,Eas}];
 encode_type(#bytes_t{len=Len}) ->
-    list_to_binary(lists:concat(["bytes(", Len, ")"]));
+    {<<"bytes">>, Len};
 encode_type(#record_t{fields=Fs}) ->
     Efs = encode_fields(Fs),
     [{<<"record">>,Efs}];
diff --git a/src/aeso_ast_to_icode.erl b/src/aeso_ast_to_icode.erl
index 41571f7..138f972 100644
--- a/src/aeso_ast_to_icode.erl
+++ b/src/aeso_ast_to_icode.erl
@@ -726,8 +726,7 @@ ttl_t(Icode) ->
     ast_typerep({qid, [], ["Chain", "ttl"]}, Icode).
 
 sign_t() -> bytes_t(64).
-bytes_t(Len) when Len =< 32 -> word;
-bytes_t(Len)                -> {tuple, lists:duplicate((31 + Len) div 32, word)}.
+bytes_t(Len) -> {bytes, Len}.
 
 get_signature_arg(Args0) ->
     NamedArgs = [Arg || Arg = {named_arg, _, _, _} <- Args0],