old_contents: # -*- coding: utf-8 -*-
  from django.db.models import F, Q
  from django.core.management.base import NoArgsCommand
  
  from modeltranslation.settings import DEFAULT_LANGUAGE
  from modeltranslation.translator import translator
  from modeltranslation.utils import build_localized_fieldname
  
  
  class Command(NoArgsCommand):
      help = ('Updates the default translation fields of all or the specified'
              'translated application using the value of the original field.')
  
      def handle(self, **options):
          print "Using default language:", DEFAULT_LANGUAGE
          for model, trans_opts in translator._registry.items():
              print "Updating data of model '%s'" % model
              for fieldname in trans_opts.fields:
                  def_lang_fieldname = build_localized_fieldname(
                      fieldname, DEFAULT_LANGUAGE)
                  # We'll only update fields which do not have an existing value
                  model.objects.filter(
                      Q(**{def_lang_fieldname: None}) |
                      Q(**{def_lang_fieldname: ""})).update(
                          **{def_lang_fieldname: F(fieldname)})
  
new_contents: # -*- coding: utf-8 -*-
  from django.db.models import F, Q
  from django.core.management.base import NoArgsCommand
  
  from modeltranslation.settings import DEFAULT_LANGUAGE
  from modeltranslation.translator import translator
  from modeltranslation.utils import build_localized_fieldname
  
  
  class Command(NoArgsCommand):
      help = ('Updates the default translation fields of all or the specified'
              'translated application using the value of the original field.')
  
      def handle(self, **options):
          verbosity = options['verbosity']
          if verbosity > 0:
              self.stdout.write("Using default language: %s\n" % DEFAULT_LANGUAGE)
          for model, trans_opts in translator._registry.items():
              if model._meta.abstract:
                  continue
              if verbosity > 0:
                  self.stdout.write("Updating data of model '%s'\n" % model)
              for fieldname in trans_opts.fields:
                  def_lang_fieldname = build_localized_fieldname(
                      fieldname, DEFAULT_LANGUAGE)
  
                  # We'll only update fields which do not have an existing value
                  q = Q(**{def_lang_fieldname: None})
                  field = model._meta.get_field(fieldname)
                  if field.empty_strings_allowed:
                      q |= Q(**{def_lang_fieldname: ""})
  
                  model.objects.filter(q).rewrite(False).update(**{def_lang_fieldname: F(fieldname)})
  
subject: Fix update_translation_fields command.