diff --git a/lib/vagrant/config/vm.rb b/lib/vagrant/config/vm.rb
index 8a4b9e249..4b9d5174b 100644
--- a/lib/vagrant/config/vm.rb
+++ b/lib/vagrant/config/vm.rb
@@ -1,3 +1,5 @@
+require 'vagrant/config/vm/sub_vm'
+
 module Vagrant
   class Config
     class VMConfig < Base
@@ -21,16 +23,6 @@ module Vagrant
       attr_writer :shared_folder_gid
       attr_accessor :system
 
-      # Represents a SubVM. This class is only used here in the VMs
-      # hash.
-      class SubVM
-        include Util::StackedProcRunner
-
-        def options
-          @options ||= {}
-        end
-      end
-
       def initialize
         @forwarded_ports = {}
         @shared_folders = {}
@@ -95,11 +87,17 @@ module Vagrant
       end
 
       def define(name, options=nil, &block)
+        name = name.to_sym
         options ||= {}
+
+        # Add the name to the array of VM keys. This array is used to
+        # preserve the order in which VMs are defined.
         defined_vm_keys << name
-        defined_vms[name.to_sym] ||= SubVM.new
-        defined_vms[name.to_sym].options.merge!(options)
-        defined_vms[name.to_sym].push_proc(&block)
+
+        # Add the SubVM to the hash of defined VMs
+        defined_vms[name] ||= SubVM.new
+        defined_vms[name].options.merge!(options)
+        defined_vms[name].push_proc(&block)
       end
 
       def validate(errors)
diff --git a/lib/vagrant/config/vm/sub_vm.rb b/lib/vagrant/config/vm/sub_vm.rb
new file mode 100644
index 000000000..413a6986e
--- /dev/null
+++ b/lib/vagrant/config/vm/sub_vm.rb
@@ -0,0 +1,17 @@
+module Vagrant
+  class Config
+    class VMConfig < Base
+      # Represents a single sub-VM in a multi-VM environment.
+      class SubVM
+        include Util::StackedProcRunner
+
+        attr_reader :options
+
+        def initialize
+          @options = {}
+        end
+      end
+    end
+  end
+end
+