Symbol not found: __mh_bundle_header

[jfirebaugh]

OS X 10.7.2, MRI 1.8.7-p249 via RVM, everything compiled with GCC 4.2, require "memprof" produces:

LoadError: dlopen(/Users/john/.rvm/gems/ruby-1.8.7-p249/gems/memprof-0.3.10/lib/memprof.bundle, 9): Symbol not found: __mh_bundle_header
  Referenced from: /Users/john/.rvm/gems/ruby-1.8.7-p249/gems/memprof-0.3.10/lib/memprof.bundle
  Expected in: flat namespace
 in /Users/john/.rvm/gems/ruby-1.8.7-p249/gems/memprof-0.3.10/lib/memprof.bundle - /Users/john/.rvm/gems/ruby-1.8.7-p249/gems/memprof-0.3.10/lib/memprof.bundle
    from /Users/john/.rvm/gems/ruby-1.8.7-p249/gems/memprof-0.3.10/lib/memprof.bundle
    from /Users/john/.rvm/rubies/ruby-1.8.7-p249/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:59:in `require'
    from (irb):6

I followed the advice of this SO answer to get it to work.