Don't set the project type explicitly, instead default it to :stand_alone via the configuration object.

lib/compass/commands/installer_command.rb

@@ -13,7 +13,7 @@ module Compass
       end
 
       def installer
-        @installer ||= case options[:project_type]
+        @installer ||= case Compass.configuration.project_type
         when :stand_alone
           StandAloneInstaller.new *installer_args
         when :rails

lib/compass/configuration/defaults.rb

@@ -2,6 +2,10 @@ module Compass
   module Configuration
     module Defaults
 
+      def default_project_type
+        :stand_alone
+      end
+
       def http_path_without_default
         "/"
       end

lib/compass/exec.rb

@@ -68,7 +68,6 @@ module Compass
         end
         self.options[:command] ||= self.options[:project_name] ? :create_project : :update_project
         self.options[:framework] ||= :compass
-        self.options[:project_type] ||= :stand_alone
       end
 
       def trim_trailing_separator(path)