diff --git a/cmd/tfinstall/main.go b/cmd/tfinstall/main.go
index 1c33f27c..8b7d934e 100644
--- a/cmd/tfinstall/main.go
+++ b/cmd/tfinstall/main.go
@@ -12,6 +12,7 @@ import (
 	"github.com/mitchellh/cli"
 
 	"github.com/hashicorp/terraform-exec/tfinstall"
+	"github.com/hashicorp/terraform-exec/tfinstall/gitref"
 )
 
 // TODO: add versioning to this?
@@ -110,7 +111,7 @@ func run(ui cli.Ui, args []string) int {
 		finder.UserAgent = userAgentAppend
 		findArgs = append(findArgs, finder)
 	case strings.HasPrefix(tfVersion, "refs/"):
-		findArgs = append(findArgs, tfinstall.GitRef(tfVersion, "", tfDir))
+		findArgs = append(findArgs, gitref.Install(tfVersion, "", tfDir))
 	default:
 		if strings.HasPrefix(tfVersion, "v") {
 			tfVersion = tfVersion[1:]
diff --git a/tfexec/internal/testutil/tfcache.go b/tfexec/internal/testutil/tfcache.go
index 3826a4ea..38e03de3 100644
--- a/tfexec/internal/testutil/tfcache.go
+++ b/tfexec/internal/testutil/tfcache.go
@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"github.com/hashicorp/terraform-exec/tfinstall"
+	"github.com/hashicorp/terraform-exec/tfinstall/gitref"
 )
 
 const (
@@ -32,7 +33,7 @@ func NewTFCache(dir string) *TFCache {
 func (tf *TFCache) GitRef(t *testing.T, ref string) string {
 	t.Helper()
 	return tf.find(t, "gitref:"+ref, func(dir string) tfinstall.ExecPathFinder {
-		return tfinstall.GitRef(ref, "", dir)
+		return gitref.Install(ref, "", dir)
 	})
 }
 
diff --git a/tfinstall/git_ref.go b/tfinstall/gitref/git_ref.go
similarity index 78%
rename from tfinstall/git_ref.go
rename to tfinstall/gitref/git_ref.go
index 71149bd4..0dc01170 100644
--- a/tfinstall/git_ref.go
+++ b/tfinstall/gitref/git_ref.go
@@ -1,4 +1,4 @@
-package tfinstall
+package gitref
 
 import (
 	"context"
@@ -14,23 +14,21 @@ import (
 	"github.com/go-git/go-git/v5/plumbing"
 )
 
-type GitRefOption struct {
+type Option struct {
 	installDir string
 	repoURL    string
 	ref        string
 }
 
-var _ ExecPathFinder = &GitRefOption{}
-
-func GitRef(ref, repo, installDir string) *GitRefOption {
-	return &GitRefOption{
+func Install(ref, repo, installDir string) *Option {
+	return &Option{
 		installDir: installDir,
 		repoURL:    repo,
 		ref:        ref,
 	}
 }
 
-func (opt *GitRefOption) ExecPath(ctx context.Context) (string, error) {
+func (opt *Option) ExecPath(ctx context.Context) (string, error) {
 	installDir, err := ensureInstallDir(opt.installDir)
 	if err != nil {
 		return "", err
@@ -91,3 +89,15 @@ func (opt *GitRefOption) ExecPath(ctx context.Context) (string, error) {
 
 	return binName, nil
 }
+
+func ensureInstallDir(installDir string) (string, error) {
+	if installDir == "" {
+		return ioutil.TempDir("", "tfexec")
+	}
+
+	if _, err := os.Stat(installDir); err != nil {
+		return "", fmt.Errorf("could not access directory %s for installing Terraform: %w", installDir, err)
+	}
+
+	return installDir, nil
+}
diff --git a/tfinstall/git_ref_test.go b/tfinstall/gitref/git_ref_test.go
similarity index 85%
rename from tfinstall/git_ref_test.go
rename to tfinstall/gitref/git_ref_test.go
index a49fc975..7e5bf149 100644
--- a/tfinstall/git_ref_test.go
+++ b/tfinstall/gitref/git_ref_test.go
@@ -1,4 +1,4 @@
-package tfinstall
+package gitref_test
 
 import (
 	"context"
@@ -7,8 +7,14 @@ import (
 	"os/exec"
 	"strings"
 	"testing"
+
+	"github.com/hashicorp/terraform-exec/tfinstall"
+	"github.com/hashicorp/terraform-exec/tfinstall/gitref"
 )
 
+// ensure the option satisfies the interface
+var _ tfinstall.ExecPathFinder = &gitref.Option{}
+
 func TestGitRef(t *testing.T) {
 	if testing.Short() {
 		t.Skip("skipping git ref tests for short run")
@@ -49,7 +55,7 @@ func TestGitRef(t *testing.T) {
 			})
 
 			t.Logf("finding / building ref %q...", c.ref)
-			tfpath, err := Find(ctx, GitRef(c.ref, "", tmpDir))
+			tfpath, err := tfinstall.Find(ctx, gitref.Install(c.ref, "", tmpDir))
 			if err != nil {
 				t.Fatalf("%T %s", err, err)
 			}