How to use TransportAddressIPv4 in conjunction with TransportAddressType as a pair?

[bbe]

@bmk

myTransport OBJECT-TYPE
    SYNTAX     MyTransport
    MAX-ACCESS not-accessible
    STATUS     current
    DESCRIPTION
            "BLA BLA BLA."
    ::= { myObject 8 }

MyTransport ::= SEQUENCE {
    type   TransportAddressType,
    addr   TransportAddress
}

Unfortunately compilation of the SEQUENCE example fails:

% rebar3 compile              
===> Verifying dependencies...
===> Analyzing applications...
MY-MIB.mib: 709: Undefined type ''MyTransport''
[MY-MIB.mib:731][WAR]: Unexpected SEQUENCE 'MyTransport' => ignoring

I suppose I could use that construction if I just can get it to compile, but in any case I’d prefer a solution using CHOICE. I have also not been able to find any examples with the CHOICE construct. Anyone else…?