django admin search with multiple words

I have troubles using the search_fields when the search expression has multiple words and i want to perform a startswith search

I have a class

class Foo(models.Model):
  kw = models.CharField(max_length = 255)
  ...

class FooAdmin(admin.ModelAdmin):
  search_fields = ('^kw',)

The '^' indicates that i want to perform a startswith search. If i'm looking for the kw 'foo fuu', django will perform the query:

select * from app_foo where `foo`.`kw` like 'foo%' and `foo`.`kw` like 'fuu%' 

This query obviously gives zero results. What should i do to make the engine looking for 'foo fuu%' ?