symfony 1.4 - all routing values being deleted when one is set in factories.yml

Question

for development/ production purposes I am setting this in factories.yml

all:
  routing:
    class: sfPatternRouting
    param:
      generate_shortest_url:            true
      logging:    false
      extra_parameters_as_query_string: true
      context:
        host: www.mydomain.com

Unfortunately this results in everything that would normally be in the routing context being overwritten so things like prefix, referrer etc are missing so:

WITHOUT this context being set in factories.yml. when you look at the routing you get a full set of context variables

object(sfRoute)[31]
protected 'isBound' => boolean true
protected 'context' => 
array
  'path_info' => string '/login' (length=6)
  'prefix' => string '/clients' (length=8)
  'method' => string 'GET' (length=3)
  'format' => null
  'host' => string 'www.domain.com' 
  'is_secure' => boolean false
  'request_uri' => string 'http:/www.domain.com/clients/login' 
 protected 'parameters' => 
array
  'module' => string 'sfGuardAuth' (length=11)
........

But WITH THIS factories.yml setting all the context variables except the host (which is what I explicitly set in factories.yml) is missing

object(sfRoute)[47]
 protected 'isBound' => boolean true
  protected 'context' => 
array
      'host' => string 'www.newdomain.com' 
protected 'parameters' => 
array
  'module' => string 'sfGuardAuth' (length=11)

.....

Does anyone know a way to set this 'host' context variable without it wiping everything else out?