diff --git a/lib/vagrant/config/top.rb b/lib/vagrant/config/top.rb
index 4d49c290a..8c2d0e5f4 100644
--- a/lib/vagrant/config/top.rb
+++ b/lib/vagrant/config/top.rb
@@ -7,8 +7,9 @@ module Vagrant
     #
     # If you're looking to create your own configuration class, see {Base}.
     class Top < Base
-      def initialize
+      def initialize(registry=nil)
         @keys = {}
+        @registry = registry || Vagrant.config_keys
       end
 
       # We use method_missing as a way to get the configuration that is used
@@ -16,7 +17,7 @@ module Vagrant
       def method_missing(name, *args)
         return @keys[name] if @keys.has_key?(name)
 
-        config_klass = Vagrant.config_keys.get(name.to_sym)
+        config_klass = @registry.get(name.to_sym)
         if config_klass
           # Instantiate the class and return the instance
           @keys[name] = config_klass.new
diff --git a/test/unit/vagrant/config/top_test.rb b/test/unit/vagrant/config/top_test.rb
new file mode 100644
index 000000000..21daf8c8e
--- /dev/null
+++ b/test/unit/vagrant/config/top_test.rb
@@ -0,0 +1,27 @@
+require File.expand_path("../../../base", __FILE__)
+
+require "vagrant/registry"
+
+describe Vagrant::Config::Top do
+  include_context "unit"
+
+  let(:registry) { Vagrant::Registry.new }
+  let(:instance) { described_class.new(registry) }
+
+  it "should load in the proper config class" do
+    registry.register(:foo, Object)
+
+    instance.foo.should be_kind_of(Object)
+  end
+
+  it "should load the proper config class only once" do
+    registry.register(:foo, Object)
+
+    obj = instance.foo
+    instance.foo.should eql(obj)
+  end
+
+  it "still raises a method missing error if invalid key" do
+    expect { instance.foo }.to raise_error(NoMethodError)
+  end
+end