diff --git a/builder/vmware/iso/builder.go b/builder/vmware/iso/builder.go
index 617e1579b..4c8e74810 100755
--- a/builder/vmware/iso/builder.go
+++ b/builder/vmware/iso/builder.go
@@ -202,6 +202,13 @@ func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 		}
 	}
 
+	if b.config.Format != "" {
+		if !(b.config.Format == "ova" || b.config.Format == "ovf" || b.config.Format == "vmx") {
+			errs = packer.MultiErrorAppend(errs,
+				fmt.Errorf("format must be one of ova, ovf, or vmx"))
+		}
+	}
+
 	// Warnings
 	if b.config.ISOChecksumType == "none" {
 		warnings = append(warnings,
diff --git a/builder/vmware/iso/builder_test.go b/builder/vmware/iso/builder_test.go
index 13a9622f7..ecc012fe0 100644
--- a/builder/vmware/iso/builder_test.go
+++ b/builder/vmware/iso/builder_test.go
@@ -208,6 +208,36 @@ func TestBuilderPrepare_FloppyFiles(t *testing.T) {
 	}
 }
 
+func TestBuilderPrepare_Format(t *testing.T) {
+	var b Builder
+	config := testConfig()
+
+	// Bad
+	config["format"] = "foobar"
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
+	if err == nil {
+		t.Fatal("should have error")
+	}
+
+	goodFormats := []string{"ova", "ovf", "vmx"}
+
+	for _, format := range goodFormats {
+		// Good
+		config["format"] = format
+		b = Builder{}
+		warns, err = b.Prepare(config)
+		if len(warns) > 0 {
+			t.Fatalf("bad: %#v", warns)
+		}
+		if err != nil {
+			t.Fatalf("should not have error: %s", err)
+		}
+	}
+}
+
 func TestBuilderPrepare_HTTPPort(t *testing.T) {
 	var b Builder
 	config := testConfig()
diff --git a/builder/vmware/iso/step_export_test.go b/builder/vmware/iso/step_export_test.go
new file mode 100644
index 000000000..9ea0d64b9
--- /dev/null
+++ b/builder/vmware/iso/step_export_test.go
@@ -0,0 +1,34 @@
+package iso
+
+import (
+	"github.com/mitchellh/multistep"
+	"testing"
+)
+
+func TestStepExport_impl(t *testing.T) {
+	var _ multistep.Step = new(StepExport)
+}
+
+func testStepExport_wrongtype_impl(t *testing.T, remoteType string) {
+	state := testState(t)
+	step := new(StepExport)
+
+	var config Config
+	config.RemoteType = "foo"
+	state.Put("config", &config)
+
+	if action := step.Run(state); action != multistep.ActionContinue {
+		t.Fatalf("bad action: %#v", action)
+	}
+	if _, ok := state.GetOk("error"); ok {
+		t.Fatal("should NOT have error")
+	}
+
+	// Cleanup
+	step.Cleanup(state)
+}
+
+func TestStepExport_wrongtype_impl(t *testing.T) {
+	testStepExport_wrongtype_impl(t, "foo")
+	testStepExport_wrongtype_impl(t, "")
+}