Binarylogic Searchlogic

It seems to me that the order in which the named scopes are applied does matter:

>> s = Task.open_or_assigned_to(employee).search
=> #<Searchlogic::Search:0x215f598 @current_scope={:conditions=>["(employee_id = ? AND state = 'assigned') OR \n      (employee_id IS NULL AND state = 'open')", 2]}, @klass=Task(id: integer, name: string, due_date: date, creator_id: integer, project_id: integer, employee_id: integer, state: string, created_at: datetime, updated_at: datetime)>

>> s.completed
=> nil

>> s = Task.completed.search
=> #<Searchlogic::Search:0x215afd4 @current_scope={:conditions=>{:state=>"completed"}}, @klass=Task(id: integer, name: string, due_date: date, creator_id: integer, project_id: integer, employee_id: integer, state: string, created_at: datetime, updated_at: datetime)>

>> s.open_or_assigned_to(employee)
=> #<Searchlogic::Search:0x215afd4 @conditions={:open_or_assigned_to=>#<Employee id: 2, first_name: "Christoph", last_name: "Lipautz", active: true, user_id: 2, created_at: "2009-06-20 20:15:25", updated_at: "2009-06-20 20:15:25">}, @current_scope={:conditions=>{:state=>"completed"}}, @klass=Task(id: integer, name: string, due_date: date, creator_id: integer, project_id: integer, employee_id: integer, state: string, created_at: datetime, updated_at: datetime)>

However,
Task.open_or_assigned_to(employee).completed.search and Task.completed.open_or_assigned_to(employee).search both work fine.

The named scope open_or_assigned_to looks like this:

  named_scope :open_or_assigned_to, lambda { |employee| { :conditions => 
    ["(employee_id = ? AND state = 'assigned') OR 
      (employee_id IS NULL AND state = 'open')", employee.id]} }