diff --git a/pkg/commands/models/commit.go b/pkg/commands/models/commit.go
index 77ad21b4a..41d19bf37 100644
--- a/pkg/commands/models/commit.go
+++ b/pkg/commands/models/commit.go
@@ -12,6 +12,15 @@ import (
 const EmptyTreeCommitHash = "4b825dc642cb6eb9a060e54bf8d69288fbee4904"
 const EmptyTreeCommitHashSHA256 = "6ef19b41225c5369f1c104d45d8d85efa9b057b53b14b4b9b939dd74decc5321"
 
+// EmptyTreeHashForFormat returns the empty tree hash for the given object
+// format ("sha1" or "sha256"). Falls back to SHA-1 for unknown formats.
+func EmptyTreeHashForFormat(objectFormat string) string {
+	if objectFormat == "sha256" {
+		return EmptyTreeCommitHashSHA256
+	}
+	return EmptyTreeCommitHash
+}
+
 type CommitStatus uint8
 
 const (
@@ -129,9 +138,11 @@ func (c *Commit) ParentRefName() string {
 }
 
 // emptyTreeHash returns the empty tree object hash matching this repo's
-// object format. SHA-256 repos produce 64-char hashes; SHA-1 repos 40-char.
+// object format. This is only called when IsFirstCommit() is true, so the
+// commit comes from git log with a full-length hash (40 for SHA-1, 64 for
+// SHA-256).
 func (c *Commit) emptyTreeHash() string {
-	if len(c.Hash()) > 40 {
+	if len(c.Hash()) == len(EmptyTreeCommitHashSHA256) {
 		return EmptyTreeCommitHashSHA256
 	}
 	return EmptyTreeCommitHash
diff --git a/pkg/gui/presentation/graph/graph.go b/pkg/gui/presentation/graph/graph.go
index 8c6a96b5e..30695c97f 100644
--- a/pkg/gui/presentation/graph/graph.go
+++ b/pkg/gui/presentation/graph/graph.go
@@ -32,9 +32,10 @@ type Pipe struct {
 }
 
 var (
-	highlightStyle      = style.FgLightWhite.SetBold()
-	EmptyTreeCommitHash = models.EmptyTreeCommitHash
-	StartCommitHash     = "START"
+	highlightStyle            = style.FgLightWhite.SetBold()
+	EmptyTreeCommitHash       = models.EmptyTreeCommitHash
+	EmptyTreeCommitHashSHA256 = models.EmptyTreeCommitHashSHA256
+	StartCommitHash           = "START"
 )
 
 func (self Pipe) left() int16 {
@@ -142,11 +143,11 @@ func getNextPipes(prevPipes []Pipe, commit *models.Commit, getStyle func(c *mode
 
 	var toHash *string
 	if commit.IsFirstCommit() {
-		emptyHash := EmptyTreeCommitHash
-		if len(commit.Hash()) > 40 {
-			emptyHash = models.EmptyTreeCommitHashSHA256
+		if len(commit.Hash()) == len(EmptyTreeCommitHashSHA256) {
+			toHash = &EmptyTreeCommitHashSHA256
+		} else {
+			toHash = &EmptyTreeCommitHash
 		}
-		toHash = &emptyHash
 	} else {
 		toHash = commit.ParentPtrs()[0]
 	}
diff --git a/pkg/gui/presentation/graph/graph_test.go b/pkg/gui/presentation/graph/graph_test.go
index a756f8aa4..0dad25ab0 100644
--- a/pkg/gui/presentation/graph/graph_test.go
+++ b/pkg/gui/presentation/graph/graph_test.go
@@ -531,6 +531,19 @@ func TestGetNextPipes(t *testing.T) {
 				{fromPos: 1, toPos: 1, fromHash: pool("root"), toHash: pool(models.EmptyTreeCommitHash), kind: STARTS, style: &style.FgDefault},
 			},
 		},
+		// SHA-256 repo: first commit with a 64-char hash should use the SHA-256 empty tree hash
+		{
+			prevPipes: []Pipe{
+				{fromPos: 0, toPos: 0, fromHash: pool("a"), toHash: pool("ba741fcd02b3cd42187ee46d4bdbfed10bf8fdbb15ccf739cb9ce583aefe5cae"), kind: TERMINATES, style: &style.FgDefault},
+			},
+			commit: models.NewCommit(hashPool, models.NewCommitOpts{
+				Hash:    "ba741fcd02b3cd42187ee46d4bdbfed10bf8fdbb15ccf739cb9ce583aefe5cae",
+				Parents: []string{},
+			}),
+			expected: []Pipe{
+				{fromPos: 1, toPos: 1, fromHash: pool("ba741fcd02b3cd42187ee46d4bdbfed10bf8fdbb15ccf739cb9ce583aefe5cae"), toHash: pool(models.EmptyTreeCommitHashSHA256), kind: STARTS, style: &style.FgDefault},
+			},
+		},
 	}
 
 	oldColorLevel := color.ForceSetColorLevel(terminfo.ColorLevelMillions)