diff --git a/lib/vagrant/box.rb b/lib/vagrant/box.rb
index e00fac2d9..41b63b292 100644
--- a/lib/vagrant/box.rb
+++ b/lib/vagrant/box.rb
@@ -58,6 +58,7 @@ module Vagrant
     # @param [Pathname] directory The directory where this box exists on
     #   disk.
     # @param [String] metadata_url Metadata URL for box
+    # @param [Hook] hook A hook to apply to the box downloader, for example, for authentication
     def initialize(name, provider, version, directory, metadata_url: nil, hook: nil)
       @name      = name
       @version   = version
diff --git a/lib/vagrant/util/downloader.rb b/lib/vagrant/util/downloader.rb
index a8a0968c4..eee9744e7 100644
--- a/lib/vagrant/util/downloader.rb
+++ b/lib/vagrant/util/downloader.rb
@@ -59,7 +59,7 @@ module Vagrant
         @ca_cert     = options[:ca_cert]
         @ca_path     = options[:ca_path]
         @continue    = options[:continue]
-        @headers     = options[:headers]
+        @headers     = Array(options[:headers])
         @insecure    = options[:insecure]
         @ui          = options[:ui]
         @client_cert = options[:client_cert]
diff --git a/plugins/commands/cloud/auth/middleware/add_downloader_authentication.rb b/plugins/commands/cloud/auth/middleware/add_downloader_authentication.rb
index 2c7237c36..ae00302a7 100644
--- a/plugins/commands/cloud/auth/middleware/add_downloader_authentication.rb
+++ b/plugins/commands/cloud/auth/middleware/add_downloader_authentication.rb
@@ -13,6 +13,8 @@ module VagrantPlugins
   module CloudCommand
     class AddDownloaderAuthentication <  AddAuthentication
 
+      @@logger = Log4r::Logger.new("vagrant::clout::add_download_authentication")
+
       def call(env)
         client = Client.new(env[:env])
         token  = client.token
@@ -38,8 +40,9 @@ module VagrantPlugins
               self.class.custom_host_notified!
             end
 
-            if !Array(env[:downloader].headers).any? { |h| h.include?("Authorization") }
-              env[:downloader].headers ||= []
+            if Array(env[:downloader].headers).any? { |h| h.include?("Authorization") }
+              @@logger.info("Not adding an authentication header, one already found")
+            else
               env[:downloader].headers << "Authorization: Bearer #{token}"
             end
           end
diff --git a/test/unit/plugins/commands/cloud/auth/middleware/add_downloader_authentication_test.rb b/test/unit/plugins/commands/cloud/auth/middleware/add_downloader_authentication_test.rb
index 9def49ff1..517d789c6 100644
--- a/test/unit/plugins/commands/cloud/auth/middleware/add_downloader_authentication_test.rb
+++ b/test/unit/plugins/commands/cloud/auth/middleware/add_downloader_authentication_test.rb
@@ -36,13 +36,13 @@ describe VagrantPlugins::CloudCommand::AddDownloaderAuthentication do
 
         env[:downloader] = dwnloader
         subject.call(env)
-        expect(env[:downloader].headers.nil?).to eq(true)
+        expect(env[:downloader].headers.empty?).to eq(true)
       end
 
       it "does nothing if we aren't logged in" do
         env[:downloader] = dwnloader
         subject.call(env)
-        expect(env[:downloader].headers.nil?).to eq(true)
+        expect(env[:downloader].headers.empty?).to eq(true)
       end
     end
 
@@ -117,7 +117,7 @@ describe VagrantPlugins::CloudCommand::AddDownloaderAuthentication do
           subject.call(env)
           
           expect(env[:downloader].source).to eq(file_path)
-          expect(env[:downloader].headers).to eq(nil)
+          expect(env[:downloader].headers.empty?).to eq(true)
         end
       end
 
@@ -149,7 +149,7 @@ describe VagrantPlugins::CloudCommand::AddDownloaderAuthentication do
       VagrantPlugins::CloudCommand::Client.new(iso_env).store_token(token)
       env[:downloader] = dwnloader
       subject.call(env)
-      expect(env[:downloader].headers).to eq(nil)
+      expect(env[:downloader].headers.empty?).to eq(true)
     end
   end
 end