diff --git a/lib/vagrant/action/builder.rb b/lib/vagrant/action/builder.rb
index 54f77a3e7..c467de445 100644
--- a/lib/vagrant/action/builder.rb
+++ b/lib/vagrant/action/builder.rb
@@ -31,15 +31,22 @@ module Vagrant
         @stack ||= []
       end
 
+      # Returns a mergeable version of the builder. If `use` is called with
+      # the return value of this method, then the stack will merge, instead
+      # of being treated as a separate single middleware.
+      def mergeable
+        [:merge, self]
+      end
+
       # Adds a middleware class to the middleware stack. Any additional
       # args and a block, if given, are saved and passed to the initializer
       # of the middleware.
       #
       # @param [Class] middleware The middleware class
       def use(middleware, *args, &block)
-        if middleware.kind_of?(Builder)
+        if middleware.kind_of?(Array) && middleware[0] == :merge
           # Merge in the other builder's stack into our own
-          self.stack.concat(middleware.stack)
+          self.stack.concat(middleware[1].stack)
         else
           self.stack << [middleware, args, block]
         end
@@ -104,7 +111,23 @@ module Vagrant
         # middleware.
         items = items.collect do |item|
           klass, args, block = item
-          lambda { |app| klass.new(app, env, *args, &block) }
+
+          lambda do |app|
+            if klass.is_a?(Class)
+              # A middleware klass which is to be instantiated with the
+              # app, env, and any arguments given
+              klass.new(app, env, *args, &block)
+            elsif klass.respond_to?(:call)
+              # Make it a lambda which calls the item then forwards
+              # up the chain
+              lambda do |e|
+                klass.call(e)
+                app.call(e)
+              end
+            else
+              raise "Invalid middleware: #{item.inspect}"
+            end
+          end
         end
 
         # Append the final step and convert into flattened call chain.
diff --git a/test/vagrant/action/builder_test.rb b/test/vagrant/action/builder_test.rb
index 5f71e7aac..ffac098fd 100644
--- a/test/vagrant/action/builder_test.rb
+++ b/test/vagrant/action/builder_test.rb
@@ -41,9 +41,26 @@ class ActionBuilderTest < Test::Unit::TestCase
         end
 
         @instance.use 1
-        @instance.use other
+        @instance.use other.mergeable
         assert_equal 3, @instance.stack.length
       end
+
+      should "not merge in another builder if not mergeable" do
+        other = @klass.new do
+          use 2
+          use 3
+        end
+
+        @instance.use 1
+        @instance.use other
+        assert_equal 2, @instance.stack.length
+      end
+    end
+
+    context "mergeable" do
+      should "return the merge format with the builder" do
+        assert_equal [:merge, @instance], @instance.mergeable
+      end
     end
 
     context "inserting" do
@@ -131,12 +148,29 @@ class ActionBuilderTest < Test::Unit::TestCase
         result = mock("result")
         env = {:a => :b}
         middleware = mock("middleware")
+        middleware.stubs(:is_a?).with(Class).returns(true)
         middleware.expects(:new).with(anything, env).returns(result)
         @instance.use middleware
         result = @instance.to_app(env)
         assert result.kind_of?(Vagrant::Action::ErrorHalt)
       end
 
+      should "make non-classes lambdas" do
+        env = Vagrant::Action::Environment.new(nil)
+        env.expects(:foo).once
+
+        func = lambda { |x| x.foo }
+        @instance.use func
+        @instance.to_app(env).call(env)
+      end
+
+      should "raise exception if given invalid middleware" do
+        @instance.use 7
+        assert_raises(RuntimeError) {
+          @instance.to_app(nil)
+        }
+      end
+
       # TODO: Better testing of this method
     end
 
diff --git a/vagrant.gemspec b/vagrant.gemspec
index 575dacca1..d0263a1f2 100644
--- a/vagrant.gemspec
+++ b/vagrant.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
 
   s.required_rubygems_version = Gem::Requirement.new("> 1.3.1") if s.respond_to? :required_rubygems_version=
   s.authors = ["Mitchell Hashimoto", "John Bender"]
-  s.date = %q{2010-07-05}
+  s.date = %q{2010-07-06}
   s.default_executable = %q{vagrant}
   s.description = %q{Vagrant is a tool for building and distributing virtualized development environments.}
   s.email = ["mitchell.hashimoto@gmail.com", "john.m.bender@gmail.com"]
@@ -41,8 +41,10 @@ Gem::Specification.new do |s|
      "lib/vagrant/action/vm/boot.rb",
      "lib/vagrant/action/vm/check_guest_additions.rb",
      "lib/vagrant/action/vm/customize.rb",
+     "lib/vagrant/action/vm/destroy.rb",
      "lib/vagrant/action/vm/destroy_unused_network_interfaces.rb",
      "lib/vagrant/action/vm/forward_ports.rb",
+     "lib/vagrant/action/vm/halt.rb",
      "lib/vagrant/action/vm/import.rb",
      "lib/vagrant/action/vm/match_mac_address.rb",
      "lib/vagrant/action/vm/network.rb",
@@ -135,8 +137,10 @@ Gem::Specification.new do |s|
      "test/vagrant/action/vm/boot_test.rb",
      "test/vagrant/action/vm/check_guest_additions_test.rb",
      "test/vagrant/action/vm/customize_test.rb",
+     "test/vagrant/action/vm/destroy_test.rb",
      "test/vagrant/action/vm/destroy_unused_network_interfaces_test.rb",
      "test/vagrant/action/vm/forward_ports_test.rb",
+     "test/vagrant/action/vm/halt_test.rb",
      "test/vagrant/action/vm/import_test.rb",
      "test/vagrant/action/vm/match_mac_address_test.rb",
      "test/vagrant/action/vm/network_test.rb",
@@ -227,8 +231,10 @@ Gem::Specification.new do |s|
      "test/vagrant/action/vm/boot_test.rb",
      "test/vagrant/action/vm/check_guest_additions_test.rb",
      "test/vagrant/action/vm/customize_test.rb",
+     "test/vagrant/action/vm/destroy_test.rb",
      "test/vagrant/action/vm/destroy_unused_network_interfaces_test.rb",
      "test/vagrant/action/vm/forward_ports_test.rb",
+     "test/vagrant/action/vm/halt_test.rb",
      "test/vagrant/action/vm/import_test.rb",
      "test/vagrant/action/vm/match_mac_address_test.rb",
      "test/vagrant/action/vm/network_test.rb",