When handling collisions, the fixer won't set the port to something which is used by that VM later

lib/vagrant/actions/vm/forward_ports.rb

@@ -41,9 +41,11 @@ module Vagrant
             raise ActionException.new(:vm_port_collision, :name => name, :hostport => options[:hostport].to_s, :guestport => options[:guestport].to_s, :adapter => options[:adapter])
           end
 
-          # Get the auto port range and get rid of the used ports so
+          # Get the auto port range and get rid of the used ports and
-          # all we're left with is available ports
+          # ports which are being used in other forwards so we're just
+          # left with available ports.
           range = runner.env.config.vm.auto_port_range.to_a
+          range -= runner.env.config.vm.forwarded_ports.collect { |n, o| o[:hostport].to_i }
           range -= used_ports
 
           if range.empty?

test/vagrant/actions/vm/forward_ports_test.rb

@@ -94,6 +94,14 @@ class ForwardPortsActionTest < Test::Unit::TestCase
       assert @used_ports.include?(4)
     end
 
+    should "not use a host port which is being forwarded later" do
+      @runner.env.config.vm.forward_port("http", 80, 4)
+
+      assert_equal 0, @options[:hostport]
+      @action.handle_collision(@name, @options, @used_ports)
+      assert_equal 5, @options[:hostport]
+    end
+
     should "raise an exception if there are no auto ports available" do
       @runner.env.config.vm.auto_port_range = (1..3)
       assert_raises(Vagrant::Actions::ActionException) {