rb18-rake conflicts with rb-rake

[barracuda156]

x ./opt/local/libexec/ruby1.8/rake
Error: Failed to activate rb18-rake: Image error: /opt/local/bin/rake-1.8 is being used by the active rb-rake port.  Please deactivate this port first, or use 'port -f activate rb18-rake' to force the activation.
    while executing
"throw registry::image-error $msg"
    ("foreach" body line 47)
    invoked from within
"foreach file $imagefiles {
                set srcfile "${extracted_dir}${file}"

                # To be able to install links, we test if we can lst..."
    invoked from within
"registry::write {
            foreach file $imagefiles {
                set srcfile "${extracted_dir}${file}"

                # To be able to instal..."
Error: See /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_ruby_rb-rake/rb18-rake/main.log for details.