Built-in plugins use Vagrant.plugin("1", :config)

plugins/guests/freebsd/config.rb

@@ -1,6 +1,6 @@
 module VagrantPlugins
   module GuestFreeBSD
-    class Config < Vagrant::Plugin::V1::Config
+    class Config < Vagrant.plugin("1", :config)
       attr_accessor :halt_timeout
       attr_accessor :halt_check_interval
 

plugins/guests/linux/config.rb

@@ -1,6 +1,6 @@
 module VagrantPlugins
   module GuestLinux
-    class Config < Vagrant::Plugin::V1::Config
+    class Config < Vagrant.plugin("1", :config)
       attr_accessor :halt_timeout
       attr_accessor :halt_check_interval
 

plugins/guests/solaris/config.rb

@@ -1,6 +1,6 @@
 module VagrantPlugins
   module GuestSolaris
-    class Config < Vagrant::Plugin::V1::Config
+    class Config < Vagrant.plugin("1", :config)
       attr_accessor :halt_timeout
       attr_accessor :halt_check_interval
       # This sets the command to use to execute items as a superuser. sudo is default

plugins/kernel_v1/config/nfs.rb

@@ -2,7 +2,7 @@ require "vagrant"
 
 module VagrantPlugins
   module Kernel_V1
-    class NFSConfig < Vagrant::Plugin::V1::Config
+    class NFSConfig < Vagrant.plugin("1", :config)
       attr_accessor :map_uid
       attr_accessor :map_gid
     end

plugins/kernel_v1/config/package.rb

@@ -2,7 +2,7 @@ require "vagrant"
 
 module VagrantPlugins
   module Kernel_V1
-    class PackageConfig < Vagrant::Plugin::V1::Config
+    class PackageConfig < Vagrant.plugin("1", :config)
       attr_accessor :name
     end
   end

plugins/kernel_v1/config/ssh.rb

@@ -2,7 +2,7 @@ require "vagrant"
 
 module VagrantPlugins
   module Kernel_V1
-    class SSHConfig < Vagrant::Plugin::V1::Config
+    class SSHConfig < Vagrant.plugin("1", :config)
       attr_accessor :username
       attr_accessor :password
       attr_accessor :host

plugins/kernel_v1/config/vagrant.rb

@@ -2,7 +2,7 @@ require "vagrant"
 
 module VagrantPlugins
   module Kernel_V1
-    class VagrantConfig < Vagrant::Plugin::V1::Config
+    class VagrantConfig < Vagrant.plugin("1", :config)
       attr_accessor :dotfile_name
       attr_accessor :host
     end

plugins/kernel_v1/config/vm.rb

@@ -7,7 +7,7 @@ require File.expand_path("../vm_subvm", __FILE__)
 
 module VagrantPlugins
   module Kernel_V1
-    class VMConfig < Vagrant::Plugin::V1::Config
+    class VMConfig < Vagrant.plugin("1", :config)
       DEFAULT_VM_NAME = :default
 
       attr_accessor :name

plugins/provisioners/chef/provisioner/base.rb

@@ -79,7 +79,7 @@ module VagrantPlugins
         end
 
          # This is the configuration which is available through `config.chef`
-        class Config < Vagrant::Plugin::V1::Config
+        class Config < Vagrant.plugin("1", :config)
           # Shared config
           attr_accessor :node_name
           attr_accessor :provisioning_path

plugins/provisioners/puppet/provisioner/puppet.rb

@@ -8,7 +8,7 @@ module VagrantPlugins
       end
 
       class Puppet < Vagrant::Plugin::V1::Provisioner
-        class Config < Vagrant::Plugin::V1::Config
+        class Config < Vagrant.plugin("1", :config)
           attr_accessor :manifest_file
           attr_accessor :manifests_path
           attr_accessor :module_path

plugins/provisioners/puppet/provisioner/puppet_server.rb

@@ -6,7 +6,7 @@ module VagrantPlugins
       end
 
       class PuppetServer < Vagrant::Plugin::V1::Provisioner
-        class Config < Vagrant::Plugin::V1::Config
+        class Config < Vagrant.plugin("1", :config)
           attr_accessor :puppet_server
           attr_accessor :puppet_node
           attr_accessor :options

plugins/provisioners/shell/provisioner.rb

@@ -4,7 +4,7 @@ require "tempfile"
 module VagrantPlugins
   module Shell
     class Provisioner < Vagrant::Plugin::V1::Provisioner
-      class Config < Vagrant::Plugin::V1::Config
+      class Config < Vagrant.plugin("1", :config)
         attr_accessor :inline
         attr_accessor :path
         attr_accessor :upload_path