[strongSwan] Is IKEv2 + transport mode + NAT traversal supported?

[IPSec Interest Group]

I am trying to activate an IKEv2 transport mode tunnel that traverses a
NAT.  It appears that, rather than sending the transport mode proposal I
configured, it is instead sending tunnel mode.
IKEv2 + tunnel mode + NAT works fine.   So does IKEv1 + transport mode
without a NAT on the tunnel path, so I know I definitely have transport mode
enabled.

Here's the configuration of my connection:

conn    NATNone4Tran
        left            = 192.168.50.9
        right           = 192.168.49.5
        type            = transport
        keyexchange     = ikev2
        leftid          = @natnone4.left.com
        rightid         = @natnone4.right.com
        pfs             = no
        auto            = add
        authby          = secret
        esp             = 3des-md5


When I activate the tunnel, it fails with NO_PROPOSAL_CHOSEN because
StrongSwan has sent a request for tunnel mode, not transport mode.
>From the log, it appears this might be intentional:

Oct  5 16:37:14 linux125 charon: 13[IKE] not using transport mode,
connection NATed

Is the combination of IKEv2 + transport mode + NAT traversal supported?
If so, can you suggest what I might need to configure differently?
Thank you!
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