diff --git a/test/unit/plugins/pushes/ftp/adapter_test.rb b/test/unit/plugins/pushes/ftp/adapter_test.rb
index e929078cd..6ef07196a 100644
--- a/test/unit/plugins/pushes/ftp/adapter_test.rb
+++ b/test/unit/plugins/pushes/ftp/adapter_test.rb
@@ -39,7 +39,10 @@ describe VagrantPlugins::FTPPush::FTPAdapter do
   include_context "unit"
 
   before(:all) do
-    @server = FakeFtp::Server.new(21212, 21213)
+    @server = nil
+    with_random_port do |port1, port2|
+      @server = FakeFtp::Server.new(port1, port2)
+    end
     @server.start
   end
 
diff --git a/test/unit/plugins/pushes/ftp/push_test.rb b/test/unit/plugins/pushes/ftp/push_test.rb
index 1f6773e24..2430138bc 100644
--- a/test/unit/plugins/pushes/ftp/push_test.rb
+++ b/test/unit/plugins/pushes/ftp/push_test.rb
@@ -9,7 +9,7 @@ describe VagrantPlugins::FTPPush::Push do
   let(:env) { isolated_environment }
   let(:config) do
     double("config",
-      host:        "127.0.0.1:51234",
+      host:        "127.0.0.1:#{@port}",
       username:    "sethvargo",
       password:    "bacon",
       passive:     false,
@@ -34,7 +34,11 @@ describe VagrantPlugins::FTPPush::Push do
 
   describe "#push" do
     before(:all) do
-      @server = FakeFtp::Server.new(51234, 21213)
+      @server = nil
+      with_random_port do |port1, port2|
+        @port = port1
+        @server = FakeFtp::Server.new(port1, port2)
+      end
       @server.start
 
       @dir = Dir.mktmpdir
diff --git a/test/unit/support/shared/base_context.rb b/test/unit/support/shared/base_context.rb
index bd7f3f517..295e83b66 100644
--- a/test/unit/support/shared/base_context.rb
+++ b/test/unit/support/shared/base_context.rb
@@ -116,4 +116,18 @@ shared_context "unit" do
       ENV[key] = value
     end
   end
+
+  # This helper provides a randomly available port(s) for each argument to the
+  # block.
+  def with_random_port(&block)
+    ports = []
+
+    block.arity.times do
+      server = TCPServer.new('127.0.0.1', 0)
+      ports << server.addr[1]
+      server.close
+    end
+
+    block.call(*ports)
+  end
 end
diff --git a/test/unit/vagrant/action/builtin/box_add_test.rb b/test/unit/vagrant/action/builtin/box_add_test.rb
index 44bcbca24..cc034df02 100644
--- a/test/unit/vagrant/action/builtin/box_add_test.rb
+++ b/test/unit/vagrant/action/builtin/box_add_test.rb
@@ -42,8 +42,12 @@ describe Vagrant::Action::Builtin::BoxAdd do
     tf = Tempfile.new("vagrant")
     tf.close
 
-    port   = 21212
-    server = FakeFtp::Server.new(port, port+1)
+    port = nil
+    server = nil
+    with_random_port do |port1, port2|
+      port = port1
+      server = FakeFtp::Server.new(port1, port2)
+    end
     server.add_file(path.basename, path.read)
     server.start
     yield port