diff --git a/go.mod b/go.mod
index dec228a..0339736 100644
--- a/go.mod
+++ b/go.mod
@@ -1,5 +1,5 @@
 module golang.org/x/mod
 
-go 1.18
+go 1.22.0
 
 require golang.org/x/tools v0.13.0 // tagx:ignore
diff --git a/zip/zip.go b/zip/zip.go
index 574f83f..5aed6e2 100644
--- a/zip/zip.go
+++ b/zip/zip.go
@@ -573,7 +573,9 @@ func CreateFromDir(w io.Writer, m module.Version, dir string) (err error) {
 // VCS repository stored locally. The zip content is written to w.
 //
 // repoRoot must be an absolute path to the base of the repository, such as
-// "/Users/some-user/some-repo".
+// "/Users/some-user/some-repo". If the repository is a Git repository,
+// this path is expected to point to its worktree: it can't be a bare git
+// repo.
 //
 // revision is the revision of the repository to create the zip from. Examples
 // include HEAD or SHA sums for git repositories.
diff --git a/zip/zip_test.go b/zip/zip_test.go
index 606e7aa..106df80 100644
--- a/zip/zip_test.go
+++ b/zip/zip_test.go
@@ -1325,7 +1325,7 @@ func downloadVCSZip(t testing.TB, vcs, url, rev, subdir string) (repoDir string,
 	switch vcs {
 	case "git":
 		// Create a repository and download the revision we want.
-		if _, err := run(t, repoDir, "git", "init", "--bare"); err != nil {
+		if _, err := runWithGitDir(t, repoDir, repoDir, "git", "init", "--bare"); err != nil {
 			return "", nil, err
 		}
 		if err := os.MkdirAll(filepath.Join(repoDir, "info"), 0777); err != nil {
@@ -1342,7 +1342,7 @@ func downloadVCSZip(t testing.TB, vcs, url, rev, subdir string) (repoDir string,
 		if err := attrFile.Close(); err != nil {
 			return "", nil, err
 		}
-		if _, err := run(t, repoDir, "git", "remote", "add", "origin", "--", url); err != nil {
+		if _, err := runWithGitDir(t, repoDir, repoDir, "git", "remote", "add", "origin", "--", url); err != nil {
 			return "", nil, err
 		}
 		var refSpec string
@@ -1351,7 +1351,7 @@ func downloadVCSZip(t testing.TB, vcs, url, rev, subdir string) (repoDir string,
 		} else {
 			refSpec = fmt.Sprintf("%s:refs/dummy", rev)
 		}
-		if _, err := run(t, repoDir, "git", "fetch", "-f", "--depth=1", "origin", refSpec); err != nil {
+		if _, err := runWithGitDir(t, repoDir, repoDir, "git", "fetch", "-f", "--depth=1", "origin", refSpec); err != nil {
 			return "", nil, err
 		}
 
@@ -1368,6 +1368,7 @@ func downloadVCSZip(t testing.TB, vcs, url, rev, subdir string) (repoDir string,
 
 		cmd := exec.Command("git", "-c", "core.autocrlf=input", "-c", "core.eol=lf", "archive", "--format=zip", "--prefix=prefix/", rev, "--", subdirArg)
 		cmd.Dir = repoDir
+		cmd.Env = append(cmd.Environ(), "GIT_DIR="+repoDir)
 		cmd.Stdout = tmpZipFile
 		stderr := new(strings.Builder)
 		cmd.Stderr = stderr
@@ -1425,17 +1426,20 @@ func downloadVCSFile(t testing.TB, vcs, repo, rev, file string) ([]byte, error)
 	t.Helper()
 	switch vcs {
 	case "git":
-		return run(t, repo, "git", "cat-file", "blob", rev+":"+file)
+		return runWithGitDir(t, repo, repo, "git", "cat-file", "blob", rev+":"+file)
 	default:
 		return nil, fmt.Errorf("vcs %q not supported", vcs)
 	}
 }
 
-func run(t testing.TB, dir string, name string, args ...string) ([]byte, error) {
+func runWithGitDir(t testing.TB, gitDir, dir string, name string, args ...string) ([]byte, error) {
 	t.Helper()
 
 	cmd := exec.Command(name, args...)
 	cmd.Dir = dir
+	if gitDir != "" {
+		cmd.Env = append(cmd.Environ(), "GIT_DIR="+gitDir)
+	}
 	stderr := new(strings.Builder)
 	cmd.Stderr = stderr
 
@@ -1450,6 +1454,12 @@ func run(t testing.TB, dir string, name string, args ...string) ([]byte, error)
 	return out, err
 }
 
+func run(t testing.TB, dir string, name string, args ...string) ([]byte, error) {
+	t.Helper()
+
+	return runWithGitDir(t, "", dir, name, args...)
+}
+
 type zipFile struct {
 	name string
 	f    *zip.File