diff --git a/archives_test.go b/archives_test.go
index 4bd8225..6094d9a 100644
--- a/archives_test.go
+++ b/archives_test.go
@@ -6,6 +6,7 @@ import (
 	"bytes"
 	"compress/gzip"
 	"io"
+	"os"
 	"strings"
 	"testing"
 	"time"
@@ -382,6 +383,145 @@ func TestOpenWithPrefix(t *testing.T) {
 	}
 }
 
+// createTestZipWithDirEntries creates a zip with explicit directory entries,
+// like GitHub zipball downloads produce.
+func createTestZipWithDirEntries() []byte {
+	buf := new(bytes.Buffer)
+	w := zip.NewWriter(buf)
+
+	// Add explicit directory entry (GitHub zipballs do this)
+	header := &zip.FileHeader{
+		Name:     "project-abc123/",
+		Method:   zip.Store,
+		Modified: time.Date(2026, 3, 30, 8, 14, 47, 0, time.UTC),
+	}
+	header.SetMode(0755 | os.ModeDir)
+	_, _ = w.CreateHeader(header)
+
+	// Add explicit src/ subdirectory entry
+	srcHeader := &zip.FileHeader{
+		Name:     "project-abc123/src/",
+		Method:   zip.Store,
+		Modified: time.Date(2026, 3, 30, 8, 14, 47, 0, time.UTC),
+	}
+	srcHeader.SetMode(0755 | os.ModeDir)
+	_, _ = w.CreateHeader(srcHeader)
+
+	// Add files inside that directory
+	files := []struct {
+		name    string
+		content string
+	}{
+		{"project-abc123/README.md", "# Test"},
+		{"project-abc123/src/main.go", "package main"},
+		{"project-abc123/src/util.go", "package main"},
+	}
+
+	for _, file := range files {
+		f, _ := w.Create(file.name)
+		_, _ = f.Write([]byte(file.content))
+	}
+
+	_ = w.Close()
+	return buf.Bytes()
+}
+
+// createTestTarGzWithDirEntries creates a tar.gz with explicit directory entries,
+// like GitHub tarball downloads produce.
+func createTestTarGzWithDirEntries() []byte {
+	buf := new(bytes.Buffer)
+	gw := gzip.NewWriter(buf)
+	tw := tar.NewWriter(gw)
+
+	// Add explicit directory entries
+	for _, dir := range []string{"project-abc123/", "project-abc123/src/"} {
+		_ = tw.WriteHeader(&tar.Header{
+			Typeflag: tar.TypeDir,
+			Name:     dir,
+			Mode:     0755,
+			ModTime:  time.Date(2026, 3, 30, 8, 14, 47, 0, time.UTC),
+		})
+	}
+
+	files := []struct {
+		name    string
+		content string
+	}{
+		{"project-abc123/README.md", "# Test"},
+		{"project-abc123/src/main.go", "package main"},
+		{"project-abc123/src/util.go", "package main"},
+	}
+
+	for _, file := range files {
+		_ = tw.WriteHeader(&tar.Header{
+			Name:    file.name,
+			Size:    int64(len(file.content)),
+			Mode:    0644,
+			ModTime: time.Date(2026, 3, 30, 8, 14, 47, 0, time.UTC),
+		})
+		_, _ = tw.Write([]byte(file.content))
+	}
+
+	_ = tw.Close()
+	_ = gw.Close()
+	return buf.Bytes()
+}
+
+func assertNoDuplicates(t *testing.T, label string, files []FileInfo) {
+	t.Helper()
+	seen := map[string]int{}
+	for _, f := range files {
+		seen[f.Path]++
+	}
+	for path, count := range seen {
+		if count > 1 {
+			t.Errorf("%s: %d entries for %q, want 1", label, count, path)
+		}
+	}
+}
+
+func TestZipListDirNoDuplicatesWithExplicitDirEntries(t *testing.T) {
+	data := createTestZipWithDirEntries()
+	reader, err := openZip(bytes.NewReader(data))
+	if err != nil {
+		t.Fatalf("openZip failed: %v", err)
+	}
+	defer func() { _ = reader.Close() }()
+
+	files, err := reader.ListDir("")
+	if err != nil {
+		t.Fatalf("ListDir root failed: %v", err)
+	}
+	assertNoDuplicates(t, "ListDir root", files)
+
+	files, err = reader.ListDir("project-abc123/")
+	if err != nil {
+		t.Fatalf("ListDir subdir failed: %v", err)
+	}
+	assertNoDuplicates(t, "ListDir project-abc123/", files)
+}
+
+func TestTarListDirNoDuplicatesWithExplicitDirEntries(t *testing.T) {
+	data := createTestTarGzWithDirEntries()
+	reader, err := openTar(bytes.NewReader(data), "gzip")
+	if err != nil {
+		t.Fatalf("openTar failed: %v", err)
+	}
+	defer func() { _ = reader.Close() }()
+
+	files, err := reader.ListDir("")
+	if err != nil {
+		t.Fatalf("ListDir root failed: %v", err)
+	}
+	assertNoDuplicates(t, "ListDir root", files)
+
+	files, err = reader.ListDir("project-abc123/")
+	if err != nil {
+		t.Fatalf("ListDir subdir failed: %v", err)
+	}
+	assertNoDuplicates(t, "ListDir project-abc123/", files)
+}
+
 func TestGetStripPrefixNpm(t *testing.T) {
 	// Create npm-style archive
 	buf := new(bytes.Buffer)
diff --git a/tar.go b/tar.go
index 6c50884..a69633b 100644
--- a/tar.go
+++ b/tar.go
@@ -100,6 +100,9 @@ func (t *tarReader) ListDir(dirPath string) ([]FileInfo, error) {
 
 		// Check if this file/dir is directly in the requested directory
 		if isInDir(path, dirPath) {
+			if f.info.IsDir {
+				seenDirs[path] = true
+			}
 			files = append(files, f.info)
 			continue
 		}
diff --git a/zip.go b/zip.go
index 09e1bd9..45fad14 100644
--- a/zip.go
+++ b/zip.go
@@ -54,6 +54,9 @@ func (z *zipReader) ListDir(dirPath string) ([]FileInfo, error) {
 
 		// Check if this file/dir is directly in the requested directory
 		if isInDir(path, dirPath) {
+			if f.FileInfo().IsDir() {
+				seenDirs[path] = true
+			}
 			files = append(files, fileInfoFromZip(f))
 			continue
 		}