diff --git a/builder/vmware/common/driver_config.go b/builder/vmware/common/driver_config.go
index c28e30de0..ecd42b0f5 100644
--- a/builder/vmware/common/driver_config.go
+++ b/builder/vmware/common/driver_config.go
@@ -1,17 +1,16 @@
 package common
 
 import (
-	"fmt"
 	"os"
 
-	"github.com/mitchellh/packer/packer"
+	"github.com/mitchellh/packer/template/interpolate"
 )
 
 type DriverConfig struct {
 	FusionAppPath string `mapstructure:"fusion_app_path"`
 }
 
-func (c *DriverConfig) Prepare(t *packer.ConfigTemplate) []error {
+func (c *DriverConfig) Prepare(ctx *interpolate.Context) []error {
 	if c.FusionAppPath == "" {
 		c.FusionAppPath = os.Getenv("FUSION_APP_PATH")
 	}
@@ -19,18 +18,5 @@ func (c *DriverConfig) Prepare(t *packer.ConfigTemplate) []error {
 		c.FusionAppPath = "/Applications/VMware Fusion.app"
 	}
 
-	templates := map[string]*string{
-		"fusion_app_path": &c.FusionAppPath,
-	}
-
-	var err error
-	errs := make([]error, 0)
-	for n, ptr := range templates {
-		*ptr, err = t.Process(*ptr, nil)
-		if err != nil {
-			errs = append(errs, fmt.Errorf("Error processing %s: %s", n, err))
-		}
-	}
-
-	return errs
+	return nil
 }
diff --git a/builder/vmware/common/output_config.go b/builder/vmware/common/output_config.go
index 19be1ba00..f3427183c 100644
--- a/builder/vmware/common/output_config.go
+++ b/builder/vmware/common/output_config.go
@@ -2,33 +2,22 @@ package common
 
 import (
 	"fmt"
-	"github.com/mitchellh/packer/common"
-	"github.com/mitchellh/packer/packer"
 	"os"
+
+	"github.com/mitchellh/packer/common"
+	"github.com/mitchellh/packer/template/interpolate"
 )
 
 type OutputConfig struct {
 	OutputDir string `mapstructure:"output_directory"`
 }
 
-func (c *OutputConfig) Prepare(t *packer.ConfigTemplate, pc *common.PackerConfig) []error {
+func (c *OutputConfig) Prepare(ctx *interpolate.Context, pc *common.PackerConfig) []error {
 	if c.OutputDir == "" {
 		c.OutputDir = fmt.Sprintf("output-%s", pc.PackerBuildName)
 	}
 
-	templates := map[string]*string{
-		"output_directory": &c.OutputDir,
-	}
-
-	errs := make([]error, 0)
-	for n, ptr := range templates {
-		var err error
-		*ptr, err = t.Process(*ptr, nil)
-		if err != nil {
-			errs = append(errs, fmt.Errorf("Error processing %s: %s", n, err))
-		}
-	}
-
+	var errs []error
 	if !pc.PackerForce {
 		if _, err := os.Stat(c.OutputDir); err == nil {
 			errs = append(errs, fmt.Errorf(
diff --git a/builder/vmware/common/run_config.go b/builder/vmware/common/run_config.go
index aef49683b..2f99984b1 100644
--- a/builder/vmware/common/run_config.go
+++ b/builder/vmware/common/run_config.go
@@ -5,7 +5,7 @@ import (
 	"fmt"
 	"time"
 
-	"github.com/mitchellh/packer/packer"
+	"github.com/mitchellh/packer/template/interpolate"
 )
 
 type RunConfig struct {
@@ -22,7 +22,7 @@ type RunConfig struct {
 	BootWait time.Duration ``
 }
 
-func (c *RunConfig) Prepare(t *packer.ConfigTemplate) []error {
+func (c *RunConfig) Prepare(ctx *interpolate.Context) []error {
 	if c.RawBootWait == "" {
 		c.RawBootWait = "10s"
 	}
@@ -43,20 +43,8 @@ func (c *RunConfig) Prepare(t *packer.ConfigTemplate) []error {
 		c.VNCPortMax = 6000
 	}
 
-	templates := map[string]*string{
-		"boot_wait":      &c.RawBootWait,
-		"http_directory": &c.HTTPDir,
-	}
-
+	var errs []error
 	var err error
-	errs := make([]error, 0)
-	for n, ptr := range templates {
-		*ptr, err = t.Process(*ptr, nil)
-		if err != nil {
-			errs = append(errs, fmt.Errorf("Error processing %s: %s", n, err))
-		}
-	}
-
 	if c.RawBootWait != "" {
 		c.BootWait, err = time.ParseDuration(c.RawBootWait)
 		if err != nil {
diff --git a/builder/vmware/common/shutdown_config.go b/builder/vmware/common/shutdown_config.go
index 05e5fdfeb..83d2224c3 100644
--- a/builder/vmware/common/shutdown_config.go
+++ b/builder/vmware/common/shutdown_config.go
@@ -2,8 +2,9 @@ package common
 
 import (
 	"fmt"
-	"github.com/mitchellh/packer/packer"
 	"time"
+
+	"github.com/mitchellh/packer/template/interpolate"
 )
 
 type ShutdownConfig struct {
@@ -13,25 +14,12 @@ type ShutdownConfig struct {
 	ShutdownTimeout time.Duration ``
 }
 
-func (c *ShutdownConfig) Prepare(t *packer.ConfigTemplate) []error {
+func (c *ShutdownConfig) Prepare(ctx *interpolate.Context) []error {
 	if c.RawShutdownTimeout == "" {
 		c.RawShutdownTimeout = "5m"
 	}
 
-	templates := map[string]*string{
-		"shutdown_command": &c.ShutdownCommand,
-		"shutdown_timeout": &c.RawShutdownTimeout,
-	}
-
-	errs := make([]error, 0)
-	for n, ptr := range templates {
-		var err error
-		*ptr, err = t.Process(*ptr, nil)
-		if err != nil {
-			errs = append(errs, fmt.Errorf("Error processing %s: %s", n, err))
-		}
-	}
-
+	var errs []error
 	var err error
 	c.ShutdownTimeout, err = time.ParseDuration(c.RawShutdownTimeout)
 	if err != nil {
diff --git a/builder/vmware/common/ssh_config.go b/builder/vmware/common/ssh_config.go
index 75d0a4b75..1bd481d92 100644
--- a/builder/vmware/common/ssh_config.go
+++ b/builder/vmware/common/ssh_config.go
@@ -8,7 +8,7 @@ import (
 	"time"
 
 	commonssh "github.com/mitchellh/packer/common/ssh"
-	"github.com/mitchellh/packer/packer"
+	"github.com/mitchellh/packer/template/interpolate"
 )
 
 type SSHConfig struct {
@@ -23,7 +23,7 @@ type SSHConfig struct {
 	SSHWaitTimeout time.Duration
 }
 
-func (c *SSHConfig) Prepare(t *packer.ConfigTemplate) []error {
+func (c *SSHConfig) Prepare(ctx *interpolate.Context) []error {
 	if c.SSHPort == 0 {
 		c.SSHPort = 22
 	}
@@ -32,23 +32,7 @@ func (c *SSHConfig) Prepare(t *packer.ConfigTemplate) []error {
 		c.RawSSHWaitTimeout = "20m"
 	}
 
-	templates := map[string]*string{
-		"ssh_host":         &c.SSHHost,
-		"ssh_key_path":     &c.SSHKeyPath,
-		"ssh_password":     &c.SSHPassword,
-		"ssh_username":     &c.SSHUser,
-		"ssh_wait_timeout": &c.RawSSHWaitTimeout,
-	}
-
-	errs := make([]error, 0)
-	for n, ptr := range templates {
-		var err error
-		*ptr, err = t.Process(*ptr, nil)
-		if err != nil {
-			errs = append(errs, fmt.Errorf("Error processing %s: %s", n, err))
-		}
-	}
-
+	var errs []error
 	if c.SSHKeyPath != "" {
 		if _, err := os.Stat(c.SSHKeyPath); err != nil {
 			errs = append(errs, fmt.Errorf("ssh_key_path is invalid: %s", err))
diff --git a/builder/vmware/common/step_type_boot_command.go b/builder/vmware/common/step_type_boot_command.go
index 82e8b3e17..397b515c5 100644
--- a/builder/vmware/common/step_type_boot_command.go
+++ b/builder/vmware/common/step_type_boot_command.go
@@ -13,6 +13,7 @@ import (
 	"github.com/mitchellh/go-vnc"
 	"github.com/mitchellh/multistep"
 	"github.com/mitchellh/packer/packer"
+	"github.com/mitchellh/packer/template/interpolate"
 )
 
 const KeyLeftShift uint32 = 0xFFE1
@@ -35,7 +36,7 @@ type bootCommandTemplateData struct {
 type StepTypeBootCommand struct {
 	BootCommand []string
 	VMName      string
-	Tpl         *packer.ConfigTemplate
+	Ctx         interpolate.Context
 }
 
 func (s *StepTypeBootCommand) Run(state multistep.StateBag) multistep.StepAction {
@@ -87,7 +88,7 @@ func (s *StepTypeBootCommand) Run(state multistep.StateBag) multistep.StepAction
 
 	log.Printf("Host IP for the VMware machine: %s", hostIp)
 
-	tplData := &bootCommandTemplateData{
+	s.Ctx.Data = &bootCommandTemplateData{
 		hostIp,
 		httpPort,
 		s.VMName,
@@ -95,7 +96,7 @@ func (s *StepTypeBootCommand) Run(state multistep.StateBag) multistep.StepAction
 
 	ui.Say("Typing the boot command over VNC...")
 	for _, command := range s.BootCommand {
-		command, err := s.Tpl.Process(command, tplData)
+		command, err := interpolate.Render(command, &s.Ctx)
 		if err != nil {
 			err := fmt.Errorf("Error preparing boot command: %s", err)
 			state.Put("error", err)
diff --git a/builder/vmware/common/step_upload_tools.go b/builder/vmware/common/step_upload_tools.go
index 03387a13f..aa7dd08e7 100644
--- a/builder/vmware/common/step_upload_tools.go
+++ b/builder/vmware/common/step_upload_tools.go
@@ -2,9 +2,11 @@ package common
 
 import (
 	"fmt"
+	"os"
+
 	"github.com/mitchellh/multistep"
 	"github.com/mitchellh/packer/packer"
-	"os"
+	"github.com/mitchellh/packer/template/interpolate"
 )
 
 type toolsUploadPathTemplate struct {
@@ -15,7 +17,7 @@ type StepUploadTools struct {
 	RemoteType        string
 	ToolsUploadFlavor string
 	ToolsUploadPath   string
-	Tpl               *packer.ConfigTemplate
+	Ctx               interpolate.Context
 }
 
 func (c *StepUploadTools) Run(state multistep.StateBag) multistep.StepAction {
@@ -44,10 +46,10 @@ func (c *StepUploadTools) Run(state multistep.StateBag) multistep.StepAction {
 	}
 	defer f.Close()
 
-	tplData := &toolsUploadPathTemplate{
+	c.Ctx.Data = &toolsUploadPathTemplate{
 		Flavor: c.ToolsUploadFlavor,
 	}
-	c.ToolsUploadPath, err = c.Tpl.Process(c.ToolsUploadPath, tplData)
+	c.ToolsUploadPath, err = interpolate.Render(c.ToolsUploadPath, &c.Ctx)
 	if err != nil {
 		err := fmt.Errorf("Error preparing upload path: %s", err)
 		state.Put("error", err)
diff --git a/builder/vmware/common/tools_config.go b/builder/vmware/common/tools_config.go
index c50c22e6b..923e531bf 100644
--- a/builder/vmware/common/tools_config.go
+++ b/builder/vmware/common/tools_config.go
@@ -1,10 +1,7 @@
 package common
 
 import (
-	"fmt"
-	"text/template"
-
-	"github.com/mitchellh/packer/packer"
+	"github.com/mitchellh/packer/template/interpolate"
 )
 
 type ToolsConfig struct {
@@ -12,27 +9,10 @@ type ToolsConfig struct {
 	ToolsUploadPath   string `mapstructure:"tools_upload_path"`
 }
 
-func (c *ToolsConfig) Prepare(t *packer.ConfigTemplate) []error {
+func (c *ToolsConfig) Prepare(ctx *interpolate.Context) []error {
 	if c.ToolsUploadPath == "" {
 		c.ToolsUploadPath = "{{ .Flavor }}.iso"
 	}
 
-	templates := map[string]*string{
-		"tools_upload_flavor": &c.ToolsUploadFlavor,
-	}
-
-	var err error
-	errs := make([]error, 0)
-	for n, ptr := range templates {
-		*ptr, err = t.Process(*ptr, nil)
-		if err != nil {
-			errs = append(errs, fmt.Errorf("Error processing %s: %s", n, err))
-		}
-	}
-
-	if _, err := template.New("path").Parse(c.ToolsUploadPath); err != nil {
-		errs = append(errs, fmt.Errorf("tools_upload_path invalid: %s", err))
-	}
-
-	return errs
+	return nil
 }
diff --git a/builder/vmware/common/vmx_config.go b/builder/vmware/common/vmx_config.go
index 98bf70a31..aac16d1e0 100644
--- a/builder/vmware/common/vmx_config.go
+++ b/builder/vmware/common/vmx_config.go
@@ -1,9 +1,7 @@
 package common
 
 import (
-	"fmt"
-
-	"github.com/mitchellh/packer/packer"
+	"github.com/mitchellh/packer/template/interpolate"
 )
 
 type VMXConfig struct {
@@ -11,49 +9,6 @@ type VMXConfig struct {
 	VMXDataPost map[string]string `mapstructure:"vmx_data_post"`
 }
 
-func (c *VMXConfig) Prepare(t *packer.ConfigTemplate) []error {
-	errs := make([]error, 0)
-	newVMXData := make(map[string]string)
-	for k, v := range c.VMXData {
-		var err error
-		k, err = t.Process(k, nil)
-		if err != nil {
-			errs = append(errs,
-				fmt.Errorf("Error processing vmx_data key %s: %s", k, err))
-			continue
-		}
-
-		v, err = t.Process(v, nil)
-		if err != nil {
-			errs = append(errs,
-				fmt.Errorf("Error processing vmx_data value '%s': %s", v, err))
-			continue
-		}
-
-		newVMXData[k] = v
-	}
-	c.VMXData = newVMXData
-
-	newVMXDataPost := make(map[string]string)
-	for k, v := range c.VMXDataPost {
-		var err error
-		k, err = t.Process(k, nil)
-		if err != nil {
-			errs = append(errs,
-				fmt.Errorf("Error processing vmx_post_data key %s: %s", k, err))
-			continue
-		}
-
-		v, err = t.Process(v, nil)
-		if err != nil {
-			errs = append(errs,
-				fmt.Errorf("Error processing vmx_post_data value '%s': %s", v, err))
-			continue
-		}
-
-		newVMXDataPost[k] = v
-	}
-	c.VMXDataPost = newVMXDataPost
-
-	return errs
+func (c *VMXConfig) Prepare(ctx *interpolate.Context) []error {
+	return nil
 }
diff --git a/builder/vmware/iso/builder.go b/builder/vmware/iso/builder.go
index 674b308c9..c63bfdc8b 100644
--- a/builder/vmware/iso/builder.go
+++ b/builder/vmware/iso/builder.go
@@ -3,26 +3,29 @@ package iso
 import (
 	"errors"
 	"fmt"
-	"github.com/mitchellh/multistep"
-	vmwcommon "github.com/mitchellh/packer/builder/vmware/common"
-	"github.com/mitchellh/packer/common"
-	"github.com/mitchellh/packer/packer"
 	"io/ioutil"
 	"log"
 	"math/rand"
 	"os"
 	"strings"
 	"time"
+
+	"github.com/mitchellh/multistep"
+	vmwcommon "github.com/mitchellh/packer/builder/vmware/common"
+	"github.com/mitchellh/packer/common"
+	"github.com/mitchellh/packer/helper/config"
+	"github.com/mitchellh/packer/packer"
+	"github.com/mitchellh/packer/template/interpolate"
 )
 
 const BuilderIdESX = "mitchellh.vmware-esx"
 
 type Builder struct {
-	config config
+	config Config
 	runner multistep.Runner
 }
 
-type config struct {
+type Config struct {
 	common.PackerConfig      `mapstructure:",squash"`
 	vmwcommon.DriverConfig   `mapstructure:",squash"`
 	vmwcommon.OutputConfig   `mapstructure:",squash"`
@@ -57,31 +60,33 @@ type config struct {
 
 	RawSingleISOUrl string `mapstructure:"iso_url"`
 
-	tpl *packer.ConfigTemplate
+	ctx interpolate.Context
 }
 
 func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
-	md, err := common.DecodeConfig(&b.config, raws...)
-	if err != nil {
-		return nil, err
-	}
-
-	b.config.tpl, err = packer.NewConfigTemplate()
+	err := config.Decode(&b.config, &config.DecodeOpts{
+		Interpolate: true,
+		InterpolateFilter: &interpolate.RenderFilter{
+			Exclude: []string{
+				"boot_command",
+				"tools_upload_path",
+			},
+		},
+	}, raws...)
 	if err != nil {
 		return nil, err
 	}
-	b.config.tpl.UserVars = b.config.PackerUserVars
 
-	// Accumulate any errors
-	errs := common.CheckUnusedConfig(md)
-	errs = packer.MultiErrorAppend(errs, b.config.DriverConfig.Prepare(b.config.tpl)...)
+	// Accumulate any errors and warnings
+	var errs *packer.MultiError
+	errs = packer.MultiErrorAppend(errs, b.config.DriverConfig.Prepare(&b.config.ctx)...)
 	errs = packer.MultiErrorAppend(errs,
-		b.config.OutputConfig.Prepare(b.config.tpl, &b.config.PackerConfig)...)
-	errs = packer.MultiErrorAppend(errs, b.config.RunConfig.Prepare(b.config.tpl)...)
-	errs = packer.MultiErrorAppend(errs, b.config.ShutdownConfig.Prepare(b.config.tpl)...)
-	errs = packer.MultiErrorAppend(errs, b.config.SSHConfig.Prepare(b.config.tpl)...)
-	errs = packer.MultiErrorAppend(errs, b.config.ToolsConfig.Prepare(b.config.tpl)...)
-	errs = packer.MultiErrorAppend(errs, b.config.VMXConfig.Prepare(b.config.tpl)...)
+		b.config.OutputConfig.Prepare(&b.config.ctx, &b.config.PackerConfig)...)
+	errs = packer.MultiErrorAppend(errs, b.config.RunConfig.Prepare(&b.config.ctx)...)
+	errs = packer.MultiErrorAppend(errs, b.config.ShutdownConfig.Prepare(&b.config.ctx)...)
+	errs = packer.MultiErrorAppend(errs, b.config.SSHConfig.Prepare(&b.config.ctx)...)
+	errs = packer.MultiErrorAppend(errs, b.config.ToolsConfig.Prepare(&b.config.ctx)...)
+	errs = packer.MultiErrorAppend(errs, b.config.VMXConfig.Prepare(&b.config.ctx)...)
 	warnings := make([]string, 0)
 
 	if b.config.DiskName == "" {
@@ -137,59 +142,6 @@ func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 		b.config.RemotePort = 22
 	}
 
-	// Errors
-	templates := map[string]*string{
-		"disk_name":              &b.config.DiskName,
-		"guest_os_type":          &b.config.GuestOSType,
-		"iso_checksum":           &b.config.ISOChecksum,
-		"iso_checksum_type":      &b.config.ISOChecksumType,
-		"iso_url":                &b.config.RawSingleISOUrl,
-		"vm_name":                &b.config.VMName,
-		"vmx_template_path":      &b.config.VMXTemplatePath,
-		"remote_type":            &b.config.RemoteType,
-		"remote_host":            &b.config.RemoteHost,
-		"remote_datastore":       &b.config.RemoteDatastore,
-		"remote_cache_datastore": &b.config.RemoteCacheDatastore,
-		"remote_cache_directory": &b.config.RemoteCacheDirectory,
-		"remote_user":            &b.config.RemoteUser,
-		"remote_password":        &b.config.RemotePassword,
-	}
-
-	for n, ptr := range templates {
-		var err error
-		*ptr, err = b.config.tpl.Process(*ptr, nil)
-		if err != nil {
-			errs = packer.MultiErrorAppend(
-				errs, fmt.Errorf("Error processing %s: %s", n, err))
-		}
-	}
-
-	for i, url := range b.config.ISOUrls {
-		var err error
-		b.config.ISOUrls[i], err = b.config.tpl.Process(url, nil)
-		if err != nil {
-			errs = packer.MultiErrorAppend(
-				errs, fmt.Errorf("Error processing iso_urls[%d]: %s", i, err))
-		}
-	}
-
-	for i, command := range b.config.BootCommand {
-		if err := b.config.tpl.Validate(command); err != nil {
-			errs = packer.MultiErrorAppend(errs,
-				fmt.Errorf("Error processing boot_command[%d]: %s", i, err))
-		}
-	}
-
-	for i, file := range b.config.FloppyFiles {
-		var err error
-		b.config.FloppyFiles[i], err = b.config.tpl.Process(file, nil)
-		if err != nil {
-			errs = packer.MultiErrorAppend(errs,
-				fmt.Errorf("Error processing floppy_files[%d]: %s",
-					i, err))
-		}
-	}
-
 	if b.config.ISOChecksumType == "" {
 		errs = packer.MultiErrorAppend(
 			errs, errors.New("The iso_checksum_type must be specified."))
@@ -343,7 +295,7 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 		&vmwcommon.StepTypeBootCommand{
 			BootCommand: b.config.BootCommand,
 			VMName:      b.config.VMName,
-			Tpl:         b.config.tpl,
+			Ctx:         b.config.ctx,
 		},
 		&common.StepConnectSSH{
 			SSHAddress:     driver.SSHAddress,
@@ -355,7 +307,7 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 			RemoteType:        b.config.RemoteType,
 			ToolsUploadFlavor: b.config.ToolsUploadFlavor,
 			ToolsUploadPath:   b.config.ToolsUploadPath,
-			Tpl:               b.config.tpl,
+			Ctx:               b.config.ctx,
 		},
 		&common.StepProvision{},
 		&vmwcommon.StepShutdown{
@@ -369,7 +321,7 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 		},
 		&vmwcommon.StepCleanVMX{},
 		&StepUploadVMX{
-			RemoteType:        b.config.RemoteType,
+			RemoteType: b.config.RemoteType,
 		},
 		&vmwcommon.StepCompactDisk{
 			Skip: b.config.SkipCompaction,
@@ -440,5 +392,5 @@ func (b *Builder) validateVMXTemplatePath() error {
 		return err
 	}
 
-	return b.config.tpl.Validate(string(data))
+	return interpolate.Validate(string(data), &b.config.ctx)
 }
diff --git a/builder/vmware/iso/driver.go b/builder/vmware/iso/driver.go
index e98019a7e..2c6c7465d 100644
--- a/builder/vmware/iso/driver.go
+++ b/builder/vmware/iso/driver.go
@@ -8,7 +8,7 @@ import (
 
 // NewDriver returns a new driver implementation for this operating
 // system, or an error if the driver couldn't be initialized.
-func NewDriver(config *config) (vmwcommon.Driver, error) {
+func NewDriver(config *Config) (vmwcommon.Driver, error) {
 	drivers := []vmwcommon.Driver{}
 
 	if config.RemoteType == "" {
diff --git a/builder/vmware/iso/driver_esx5.go b/builder/vmware/iso/driver_esx5.go
index 1f9bd7a78..d81149511 100644
--- a/builder/vmware/iso/driver_esx5.go
+++ b/builder/vmware/iso/driver_esx5.go
@@ -3,13 +3,9 @@ package iso
 import (
 	"bufio"
 	"bytes"
-	gossh "code.google.com/p/go.crypto/ssh"
 	"encoding/csv"
 	"errors"
 	"fmt"
-	"github.com/mitchellh/multistep"
-	"github.com/mitchellh/packer/communicator/ssh"
-	"github.com/mitchellh/packer/packer"
 	"io"
 	"log"
 	"net"
@@ -17,6 +13,11 @@ import (
 	"path/filepath"
 	"strings"
 	"time"
+
+	gossh "code.google.com/p/go.crypto/ssh"
+	"github.com/mitchellh/multistep"
+	"github.com/mitchellh/packer/communicator/ssh"
+	"github.com/mitchellh/packer/packer"
 )
 
 // ESX5 driver talks to an ESXi5 hypervisor remotely over SSH to build
@@ -218,7 +219,7 @@ func (d *ESX5Driver) VNCAddress(portMin, portMax uint) (string, uint, error) {
 }
 
 func (d *ESX5Driver) SSHAddress(state multistep.StateBag) (string, error) {
-	config := state.Get("config").(*config)
+	config := state.Get("config").(*Config)
 
 	if address, ok := state.GetOk("vm_address"); ok {
 		return address.(string), nil
diff --git a/builder/vmware/iso/step_create_disk.go b/builder/vmware/iso/step_create_disk.go
index cade63f75..b357cad01 100644
--- a/builder/vmware/iso/step_create_disk.go
+++ b/builder/vmware/iso/step_create_disk.go
@@ -20,7 +20,7 @@ import (
 type stepCreateDisk struct{}
 
 func (stepCreateDisk) Run(state multistep.StateBag) multistep.StepAction {
-	config := state.Get("config").(*config)
+	config := state.Get("config").(*Config)
 	driver := state.Get("driver").(vmwcommon.Driver)
 	ui := state.Get("ui").(packer.Ui)
 
diff --git a/builder/vmware/iso/step_create_vmx.go b/builder/vmware/iso/step_create_vmx.go
index e490e639b..5a1a829b5 100644
--- a/builder/vmware/iso/step_create_vmx.go
+++ b/builder/vmware/iso/step_create_vmx.go
@@ -2,12 +2,14 @@ package iso
 
 import (
 	"fmt"
-	"github.com/mitchellh/multistep"
-	vmwcommon "github.com/mitchellh/packer/builder/vmware/common"
-	"github.com/mitchellh/packer/packer"
 	"io/ioutil"
 	"os"
 	"path/filepath"
+
+	"github.com/mitchellh/multistep"
+	vmwcommon "github.com/mitchellh/packer/builder/vmware/common"
+	"github.com/mitchellh/packer/packer"
+	"github.com/mitchellh/packer/template/interpolate"
 )
 
 type vmxTemplateData struct {
@@ -32,13 +34,14 @@ type stepCreateVMX struct {
 }
 
 func (s *stepCreateVMX) Run(state multistep.StateBag) multistep.StepAction {
-	config := state.Get("config").(*config)
+	config := state.Get("config").(*Config)
 	isoPath := state.Get("iso_path").(string)
 	ui := state.Get("ui").(packer.Ui)
 
 	ui.Say("Building and writing VMX file")
 
-	tplData := &vmxTemplateData{
+	ctx := config.ctx
+	ctx.Data = &vmxTemplateData{
 		Name:     config.VMName,
 		GuestOS:  config.GuestOSType,
 		DiskName: config.DiskName,
@@ -68,7 +71,7 @@ func (s *stepCreateVMX) Run(state multistep.StateBag) multistep.StepAction {
 		vmxTemplate = string(rawBytes)
 	}
 
-	vmxContents, err := config.tpl.Process(vmxTemplate, tplData)
+	vmxContents, err := interpolate.Render(vmxTemplate, &ctx)
 	if err != nil {
 		err := fmt.Errorf("Error procesing VMX template: %s", err)
 		state.Put("error", err)
diff --git a/builder/vmware/iso/step_remote_upload.go b/builder/vmware/iso/step_remote_upload.go
index 927c16c2a..1fc66a541 100644
--- a/builder/vmware/iso/step_remote_upload.go
+++ b/builder/vmware/iso/step_remote_upload.go
@@ -29,7 +29,7 @@ func (s *stepRemoteUpload) Run(state multistep.StateBag) multistep.StepAction {
 		return multistep.ActionContinue
 	}
 
-	config := state.Get("config").(*config)
+	config := state.Get("config").(*Config)
 	checksum := config.ISOChecksum
 	checksumType := config.ISOChecksumType
 
diff --git a/template/interpolate/i.go b/template/interpolate/i.go
index fa3a31395..c0cd13f85 100644
--- a/template/interpolate/i.go
+++ b/template/interpolate/i.go
@@ -27,6 +27,11 @@ func Render(v string, ctx *Context) (string, error) {
 	return (&I{Value: v}).Render(ctx)
 }
 
+// Validate is shorthand for constructing an I and calling Validate.
+func Validate(v string, ctx *Context) error {
+	return (&I{Value: v}).Validate(ctx)
+}
+
 // I stands for "interpolation" and is the main interpolation struct
 // in order to render values.
 type I struct {
@@ -52,6 +57,12 @@ func (i *I) Render(ctx *Context) (string, error) {
 	return result.String(), nil
 }
 
+// Validate validates that the template is syntactically valid.
+func (i *I) Validate(ctx *Context) error {
+	_, err := i.template(ctx)
+	return err
+}
+
 func (i *I) template(ctx *Context) (*template.Template, error) {
 	return template.New("root").Funcs(Funcs(ctx)).Parse(i.Value)
 }
diff --git a/template/interpolate/render.go b/template/interpolate/render.go
index a4c33222d..2120c171f 100644
--- a/template/interpolate/render.go
+++ b/template/interpolate/render.go
@@ -34,6 +34,11 @@ func RenderMap(v interface{}, ctx *Context, f *RenderFilter) (map[string]interfa
 
 	// Now go through each value and render it
 	for k, raw := range m {
+		// Always validate every field
+		if err := ValidateInterface(raw, ctx); err != nil {
+			return nil, fmt.Errorf("invalid '%s': %s", k, err)
+		}
+
 		if !f.include(k) {
 			continue
 		}
@@ -70,6 +75,24 @@ func RenderInterface(v interface{}, ctx *Context) (interface{}, error) {
 	return v, nil
 }
 
+// ValidateInterface renders any value and returns the resulting value.
+func ValidateInterface(v interface{}, ctx *Context) error {
+	f := func(v string) (string, error) {
+		return v, Validate(v, ctx)
+	}
+
+	walker := &renderWalker{
+		F:       f,
+		Replace: false,
+	}
+	err := reflectwalk.Walk(v, walker)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
 // Include checks whether a key should be included.
 func (f *RenderFilter) include(k string) bool {
 	if f == nil {