No need to reload the VMs hash if has a parent environment.

lib/vagrant/environment.rb

@@ -81,6 +81,7 @@ module Vagrant
 
     # Returns the VMs associated with this environment.
     def vms
+      return parent.vms if parent
       load! if !loaded?
       @vms ||= {}
     end
@@ -275,7 +276,7 @@ module Vagrant
       # This environment represents a single sub VM. The VM is then
       # probably (read: should be) set on the VM attribute, so we do
       # nothing.
-      return if vm
+      return if parent
 
       # First load the defaults (blank, noncreated VMs)
       load_blank_vms!

test/vagrant/environment_test.rb

@@ -306,6 +306,15 @@ class EnvironmentTest < Test::Unit::TestCase
       env.expects(:load!).never
       env.vms
     end
+
+    should "return the parent's VMs hash if it has one" do
+      env = vagrant_env(vagrantfile(<<-vf))
+        config.vm.define :web
+        config.vm.define :db
+      vf
+
+      assert env.vms[:web].env.vms.equal?(env.vms)
+    end
   end
 
   context "loading" do
@@ -484,10 +493,15 @@ class EnvironmentTest < Test::Unit::TestCase
         end
       end
 
-      should "do nothing if the vm is set" do
-        @env.stubs(:vm).returns(mock("vm"))
-        File.expects(:open).never
-        @env.load_vm!
+      should "do nothing if the parent is set" do
+        env = vagrant_env(vagrantfile(<<-vf))
+          config.vm.define :web
+          config.vm.define :db
+        vf
+
+        subenv = env.vms[:web].env
+        subenv.expects(:load_blank_vms!).never
+        subenv.load_vm!
       end
 
       should "uuid should be nil if local data contains nothing" do