diff --git a/packer/rpc/ui.go b/packer/rpc/ui.go
index 2a3807528..617541dde 100644
--- a/packer/rpc/ui.go
+++ b/packer/rpc/ui.go
@@ -19,8 +19,8 @@ type UiServer struct {
 
 // The arguments sent to Ui.Machine
 type UiMachineArgs struct {
-	category string
-	args     []string
+	Category string
+	Args     []string
 }
 
 func (u *Ui) Ask(query string) (result string, err error) {
@@ -36,11 +36,11 @@ func (u *Ui) Error(message string) {
 
 func (u *Ui) Machine(t string, args ...string) {
 	rpcArgs := &UiMachineArgs{
-		category: t,
-		args:     args,
+		Category: t,
+		Args:     args,
 	}
 
-	if err := u.client.Call("Ui.Message", rpcArgs, new(interface{})); err != nil {
+	if err := u.client.Call("Ui.Machine", rpcArgs, new(interface{})); err != nil {
 		panic(err)
 	}
 }
@@ -70,7 +70,7 @@ func (u *UiServer) Error(message *string, reply *interface{}) error {
 }
 
 func (u *UiServer) Machine(args *UiMachineArgs, reply *interface{}) error {
-	u.ui.Machine(args.category, args.args...)
+	u.ui.Machine(args.Category, args.Args...)
 
 	*reply = nil
 	return nil
diff --git a/packer/rpc/ui_test.go b/packer/rpc/ui_test.go
index 7dae40763..dec0d4721 100644
--- a/packer/rpc/ui_test.go
+++ b/packer/rpc/ui_test.go
@@ -3,6 +3,7 @@ package rpc
 import (
 	"cgl.tideland.biz/asserts"
 	"net/rpc"
+	"reflect"
 	"testing"
 )
 
@@ -81,4 +82,18 @@ func TestUiRPC(t *testing.T) {
 
 	uiClient.Say("message")
 	assert.Equal(ui.sayMessage, "message", "message should be correct")
+
+	uiClient.Machine("foo", "bar", "baz")
+	if !ui.machineCalled {
+		t.Fatal("machine should be called")
+	}
+
+	if ui.machineType != "foo" {
+		t.Fatalf("bad type: %#v", ui.machineType)
+	}
+
+	expected := []string{"bar", "baz"}
+	if !reflect.DeepEqual(ui.machineArgs, expected) {
+		t.Fatalf("bad: %#v", ui.machineArgs)
+	}
 }