How does one configure which partition receives the dump?

I have tried adding dump on sd4d to my config line, but config refuses
to accept this.  The default dump device on my machine seems to be
bogus.  Even it it weren't, I want the dump on sd4d.  For reference,
here is my current attempt at a config line.

config netbsd root on sd1a swap on sd0b and sd1b and sd2b and sd3b dump on sd3b

Dave.

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|David Gilbert, PCI, Richmond Hill, Ontario.  | Two things can only be     |
|Mail:      dgilbert@jaywon.pci.on.ca         |  equal if and only if they |
|http://www.pci.on.ca/~dgilbert               |   are precisely opposite.  |
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