mk bin-install: IPv4 for FTP?

I'm trying to use make bin-install to install binary packages if they're 
available from the NetBSd FTP site before installing from source.  I noticed 
that, unlike when using pkg_add, which if it doesn't connect using the IPv6 
address falls back to IPv4, make bin-install will only try the IPv6 address and 
if it fails, it just goes on to install the package from source.

Is there a way to either have make bin-install fall back to IPv4 or to set it 
to only use IPv4?

- Dave V.

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