diff --git a/lib/command.rb b/lib/command.rb
index a5496b0..3f5568f 100644
--- a/lib/command.rb
+++ b/lib/command.rb
@@ -16,6 +16,14 @@ def execute
 
         with_target_vms(argv, {:single_target=>true}) do |machine|
           ip = machine.provider.capability(:public_address)
+
+          if machine.state.id != :running
+            raise ::VagrantPlugins::CommandAddress::Errors::NotRunning
+          end
+          if ip == nil
+            raise ::VagrantPlugins::CommandAddress::Errors::Unknown
+          end
+
           message = ENV['TEAMCITY_VERSION'] ? "##teamcity[setParameter name='env.VAGRANT_ADDRESS' value='#{ip}']" : ip
           @env.ui.info(message)
         end
diff --git a/lib/errors.rb b/lib/errors.rb
new file mode 100644
index 0000000..a477eb2
--- /dev/null
+++ b/lib/errors.rb
@@ -0,0 +1,16 @@
+module VagrantPlugins
+  module CommandAddress
+    module Errors
+      class AddressError < Vagrant::Errors::VagrantError
+        error_namespace("vagrant_address.errors")
+      end
+
+      class NotRunning < AddressError
+        error_key(:not_running)
+      end
+      class Unknown < AddressError
+        error_key(:unknown)
+      end
+    end
+  end
+end
diff --git a/lib/locales/en.yml b/lib/locales/en.yml
new file mode 100644
index 0000000..ae4c095
--- /dev/null
+++ b/lib/locales/en.yml
@@ -0,0 +1,7 @@
+en:
+  vagrant_address:
+    errors:
+      not_running: |-
+        A machine is not running
+      unknown: |-
+        The address is unknown. Refer to https://github.com/mkuzmin/vagrant-address/issues/5
diff --git a/lib/vagrant-address.rb b/lib/vagrant-address.rb
index 7919d79..d910f19 100644
--- a/lib/vagrant-address.rb
+++ b/lib/vagrant-address.rb
@@ -2,6 +2,8 @@
 
 module VagrantPlugins
   module CommandAddress
+    autoload :Errors, File.expand_path("../errors", __FILE__)
+
     class Plugin < Vagrant.plugin("2")
       name "address"
       description <<-DESC
@@ -10,8 +12,19 @@ class Plugin < Vagrant.plugin("2")
 
       command("address", primary: false) do
         require_relative "command"
+        init!
         Command
       end
+
+      protected
+
+      def self.init!
+        return if defined?(@_init)
+        I18n.load_path << File.expand_path("../locales/en.yml", __FILE__)
+        I18n.reload!
+        @_init = true
+      end
+
     end
   end
 end
diff --git a/vagrant-address.gemspec b/vagrant-address.gemspec
index ee3e3ef..532db94 100644
--- a/vagrant-address.gemspec
+++ b/vagrant-address.gemspec
@@ -1,6 +1,6 @@
 Gem::Specification.new do |spec|
   spec.name          = 'vagrant-address'
-  spec.version       = '0.3'
+  spec.version       = '0.3.1'
   spec.authors       = ['Michael Kuzmin']
   spec.email         = ['mkuzmin@gmail.com']
   spec.summary       = 'Vagrant plugin for obtaining IP address of a guest machine'