updateSystemMetadata error: "node" is missing

[gothub]

@taojing2002 reported the following error when executing this R fragment:

mn <- MNode("https://valley.duckdns.org/metacat/d1/mn/v2")
sysmeta@obsoletedBy <- pid1
updateSystemMetadata(mn, pid, sysmeta)
Error in .local(.Object, ...) : 
  argument "node" is missing, with no default

Note that the server being used is not a registered MN with DataONE, which may or may not be a contributing factor to this issue.