--- lib/update.js.orig	2013-06-21 13:44:01.000000000 +0200
+++ lib/update.js	2013-06-26 21:18:40.000000000 +0200
@@ -35,6 +35,14 @@
         , req = ww[4]
         , url = require('url')
 
+      if (what.match(/^npm@/) && where.match(/@@NPM_PATH_JSREGEX@@/)) {
+        log.error("Trying to update '" + what + "' in '" + where + "'")
+        log.error("which is part of the MacPorts npm base installation.")
+        log.error("To update npm please run:")
+        log.error("sudo port selfupdate && sudo port upgrade npm\n")
+        return cb()
+      }
+
       // use the initial installation method (repo, tar, git) for updating
       if (url.parse(req).protocol) what = req
       npm.commands.install(where, what, cb)