diff --git a/cmd/gogit/show-index.go b/cmd/gogit/show-index.go
index 1dd3524..d738d6b 100644
--- a/cmd/gogit/show-index.go
+++ b/cmd/gogit/show-index.go
@@ -1,10 +1,13 @@
 package main
 
 import (
+	"bytes"
 	"crypto"
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
+	"time"
 
 	"github.com/go-git/go-git/v6/plumbing/format/idxfile"
 	"github.com/go-git/go-git/v6/plumbing/hash"
@@ -29,7 +32,12 @@ var showIndexCmd = &cobra.Command{
 
 func showIndexRun(in io.Reader, out io.Writer) error {
 	idx := idxfile.NewMemoryIndex(crypto.SHA1.Size())
-	dec := idxfile.NewDecoder(in, hash.New(crypto.SHA1))
+	idxIn, err := idxInput(in)
+	if err != nil {
+		return err
+	}
+
+	dec := idxfile.NewDecoder(idxIn, hash.New(crypto.SHA1))
 
 	if err := dec.Decode(idx); err != nil {
 		return fmt.Errorf("decode idx: %w", err)
@@ -56,3 +64,35 @@ func showIndexRun(in io.Reader, out io.Writer) error {
 
 	return nil
 }
+
+func idxInput(in io.Reader) (idxfile.Input, error) {
+	b, err := io.ReadAll(in)
+	if err != nil {
+		return nil, fmt.Errorf("read idx input: %w", err)
+	}
+
+	return &memoryIdxInput{
+		Reader: bytes.NewReader(b),
+		size:   int64(len(b)),
+	}, nil
+}
+
+type memoryIdxInput struct {
+	*bytes.Reader
+	size int64
+}
+
+func (in *memoryIdxInput) Stat() (fs.FileInfo, error) {
+	return memoryIdxFileInfo{size: in.size}, nil
+}
+
+type memoryIdxFileInfo struct {
+	size int64
+}
+
+func (fi memoryIdxFileInfo) Name() string       { return "" }
+func (fi memoryIdxFileInfo) Size() int64        { return fi.size }
+func (fi memoryIdxFileInfo) Mode() fs.FileMode  { return 0 }
+func (fi memoryIdxFileInfo) ModTime() time.Time { return time.Time{} }
+func (fi memoryIdxFileInfo) IsDir() bool        { return false }
+func (fi memoryIdxFileInfo) Sys() any           { return nil }
diff --git a/go.mod b/go.mod
index c3043c6..7ffc547 100644
--- a/go.mod
+++ b/go.mod
@@ -7,7 +7,7 @@ toolchain go1.25.10
 require (
 	github.com/go-git/go-billy/v6 v6.0.0-alpha.1
 	github.com/go-git/go-git-fixtures/v6 v6.0.0-alpha.1
-	github.com/go-git/go-git/v6 v6.0.0-alpha.3.0.20260512141313-533ba09d9588
+	github.com/go-git/go-git/v6 v6.0.0-alpha.4
 	github.com/spf13/cobra v1.10.2
 	golang.org/x/crypto v0.52.0
 	golang.org/x/term v0.43.0
diff --git a/go.sum b/go.sum
index 4ea6d70..9795f1e 100644
--- a/go.sum
+++ b/go.sum
@@ -22,8 +22,8 @@ github.com/go-git/go-billy/v6 v6.0.0-alpha.1 h1:xVjAR4oUvrKy7/Xuw/lLlV3gkxR3KO2H
 github.com/go-git/go-billy/v6 v6.0.0-alpha.1/go.mod h1:eaCUpHbedW7//EwcYmUDfJe2N6sJC9O12AT0OTqJR1E=
 github.com/go-git/go-git-fixtures/v6 v6.0.0-alpha.1 h1:gmqi2jvsreu0s8JMLylYDFq4sbjHwwlhktMw0DUg3mA=
 github.com/go-git/go-git-fixtures/v6 v6.0.0-alpha.1/go.mod h1:ECf1MqJlBdYpKggBrOXjo/0EnvRZx6D++I86UYjPgAQ=
-github.com/go-git/go-git/v6 v6.0.0-alpha.3.0.20260512141313-533ba09d9588 h1:TgVntrlBTW1A2HAoPljPLhP8rxmLzI4mUPv2Aq7r4KQ=
-github.com/go-git/go-git/v6 v6.0.0-alpha.3.0.20260512141313-533ba09d9588/go.mod h1:4ODa/G7hPWrh4Y+7lmt59Ij3zW38IEfvRoAZxLYYBhc=
+github.com/go-git/go-git/v6 v6.0.0-alpha.4 h1:aDTc2UGanmaE7FkGLSlBEB9nohMnQ+RKXcfq/D+esDQ=
+github.com/go-git/go-git/v6 v6.0.0-alpha.4/go.mod h1:4ODa/G7hPWrh4Y+7lmt59Ij3zW38IEfvRoAZxLYYBhc=
 github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
 github.com/kevinburke/ssh_config v1.6.0 h1:J1FBfmuVosPHf5GRdltRLhPJtJpTlMdKTBjRgTaQBFY=