fix segmentation fault in E2E when light-client feature flag is enabled (#14699)

* use `blockEpoch` in `BlockToLightClientHeader`

* deps

* dont use `EmptyExecutionPayload()`

* use original logic

* changelog

* add feature flag check

* fix

* fix error messages

* update `BlockToLightClientHeader` tests

* changelog

* deps

CHANGELOG.md

@@ -32,6 +32,7 @@ The format is based on Keep a Changelog, and this project adheres to Semantic Ve
 - Added a Prometheus error counter metric for HTTP requests to track beacon node requests.
 - Added a Prometheus error counter metric for SSE requests.
 - Save light client updates and bootstraps in DB.
+- Added more comprehensive tests for `BlockToLightClientHeader`. [PR](https://github.com/prysmaticlabs/prysm/pull/14699)
 
 ### Changed
 
@@ -112,6 +113,7 @@ The format is based on Keep a Changelog, and this project adheres to Semantic Ve
 - P2P: Avoid infinite loop when looking for peers in small networks.
 - Fixed another rollback bug due to a context deadline.
 - Fix checkpoint sync bug on holesky. [pr](https://github.com/prysmaticlabs/prysm/pull/14689)
+- Fix segmentation fault in E2E when light-client feature flag is enabled. [PR](https://github.com/prysmaticlabs/prysm/pull/14699)
 
 
 ### Security

beacon-chain/core/light-client/BUILD.bazel

@@ -6,7 +6,6 @@ go_library(
     importpath = "github.com/prysmaticlabs/prysm/v5/beacon-chain/core/light-client",
     visibility = ["//visibility:public"],
     deps = [
-        "//beacon-chain/execution:go_default_library",
         "//beacon-chain/state:go_default_library",
         "//config/fieldparams:go_default_library",
         "//config/params:go_default_library",
@@ -31,8 +30,10 @@ go_test(
     deps = [
         ":go_default_library",
         "//config/fieldparams:go_default_library",
+        "//config/params:go_default_library",
         "//consensus-types:go_default_library",
         "//consensus-types/blocks:go_default_library",
+        "//consensus-types/primitives:go_default_library",
         "//encoding/ssz:go_default_library",
         "//proto/engine/v1:go_default_library",
         "//proto/prysm/v1alpha1:go_default_library",

beacon-chain/core/light-client/lightclient.go

@@ -7,7 +7,6 @@ import (
 	"reflect"
 
 	"github.com/pkg/errors"
-	"github.com/prysmaticlabs/prysm/v5/beacon-chain/execution"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/state"
 	fieldparams "github.com/prysmaticlabs/prysm/v5/config/fieldparams"
 	"github.com/prysmaticlabs/prysm/v5/config/params"
@@ -473,15 +472,18 @@ func BlockToLightClientHeader(
 		var payloadProof [][]byte
 
 		if blockEpoch < params.BeaconConfig().CapellaForkEpoch {
-			var ok bool
-
-			p, err := execution.EmptyExecutionPayload(version.Deneb)
-			if err != nil {
-				return nil, errors.Wrap(err, "could not get payload header")
-			}
-			payloadHeader, ok = p.(*enginev1.ExecutionPayloadHeaderDeneb)
-			if !ok {
-				return nil, errors.Wrapf(err, "payload header type %T is not %T", payloadHeader, &enginev1.ExecutionPayloadHeaderDeneb{})
+			payloadHeader = &enginev1.ExecutionPayloadHeaderDeneb{
+				ParentHash:       make([]byte, fieldparams.RootLength),
+				FeeRecipient:     make([]byte, fieldparams.FeeRecipientLength),
+				StateRoot:        make([]byte, fieldparams.RootLength),
+				ReceiptsRoot:     make([]byte, fieldparams.RootLength),
+				LogsBloom:        make([]byte, fieldparams.LogsBloomLength),
+				PrevRandao:       make([]byte, fieldparams.RootLength),
+				ExtraData:        make([]byte, 0),
+				BaseFeePerGas:    make([]byte, fieldparams.RootLength),
+				BlockHash:        make([]byte, fieldparams.RootLength),
+				TransactionsRoot: make([]byte, fieldparams.RootLength),
+				WithdrawalsRoot:  make([]byte, fieldparams.RootLength),
 			}
 			payloadProof = emptyPayloadProof()
 		} else {

beacon-chain/core/light-client/lightclient_test.go

@@ -7,8 +7,10 @@ import (
 	"github.com/pkg/errors"
 	lightClient "github.com/prysmaticlabs/prysm/v5/beacon-chain/core/light-client"
 	fieldparams "github.com/prysmaticlabs/prysm/v5/config/fieldparams"
+	"github.com/prysmaticlabs/prysm/v5/config/params"
 	consensustypes "github.com/prysmaticlabs/prysm/v5/consensus-types"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/blocks"
+	"github.com/prysmaticlabs/prysm/v5/consensus-types/primitives"
 	"github.com/prysmaticlabs/prysm/v5/encoding/ssz"
 	v11 "github.com/prysmaticlabs/prysm/v5/proto/engine/v1"
 	pb "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
@@ -357,7 +359,11 @@ func TestLightClient_BlockToLightClientHeader(t *testing.T) {
 	t.Run("Altair", func(t *testing.T) {
 		l := util.NewTestLightClient(t).SetupTestAltair()
 
-		header, err := lightClient.BlockToLightClientHeader(l.Ctx, l.State.Slot(), l.Block)
+		header, err := lightClient.BlockToLightClientHeader(
+			l.Ctx,
+			primitives.Slot(params.BeaconConfig().AltairForkEpoch)*params.BeaconConfig().SlotsPerEpoch,
+			l.Block,
+		)
 		require.NoError(t, err)
 		require.NotNil(t, header, "header is nil")
 
@@ -376,7 +382,11 @@ func TestLightClient_BlockToLightClientHeader(t *testing.T) {
 	t.Run("Bellatrix", func(t *testing.T) {
 		l := util.NewTestLightClient(t).SetupTestBellatrix()
 
-		header, err := lightClient.BlockToLightClientHeader(l.Ctx, l.State.Slot(), l.Block)
+		header, err := lightClient.BlockToLightClientHeader(
+			l.Ctx,
+			primitives.Slot(params.BeaconConfig().BellatrixForkEpoch)*params.BeaconConfig().SlotsPerEpoch,
+			l.Block,
+		)
 		require.NoError(t, err)
 		require.NotNil(t, header, "header is nil")
 
@@ -396,7 +406,11 @@ func TestLightClient_BlockToLightClientHeader(t *testing.T) {
 		t.Run("Non-Blinded Beacon Block", func(t *testing.T) {
 			l := util.NewTestLightClient(t).SetupTestCapella(false)
 
-			header, err := lightClient.BlockToLightClientHeader(l.Ctx, l.State.Slot(), l.Block)
+			header, err := lightClient.BlockToLightClientHeader(
+				l.Ctx,
+				primitives.Slot(params.BeaconConfig().CapellaForkEpoch)*params.BeaconConfig().SlotsPerEpoch,
+				l.Block,
+			)
 			require.NoError(t, err)
 			require.NotNil(t, header, "header is nil")
 
@@ -453,7 +467,11 @@ func TestLightClient_BlockToLightClientHeader(t *testing.T) {
 		t.Run("Blinded Beacon Block", func(t *testing.T) {
 			l := util.NewTestLightClient(t).SetupTestCapella(true)
 
-			header, err := lightClient.BlockToLightClientHeader(l.Ctx, l.State.Slot(), l.Block)
+			header, err := lightClient.BlockToLightClientHeader(
+				l.Ctx,
+				primitives.Slot(params.BeaconConfig().CapellaForkEpoch)*params.BeaconConfig().SlotsPerEpoch,
+				l.Block,
+			)
 			require.NoError(t, err)
 			require.NotNil(t, header, "header is nil")
 
@@ -512,7 +530,11 @@ func TestLightClient_BlockToLightClientHeader(t *testing.T) {
 		t.Run("Non-Blinded Beacon Block", func(t *testing.T) {
 			l := util.NewTestLightClient(t).SetupTestDeneb(false)
 
-			header, err := lightClient.BlockToLightClientHeader(l.Ctx, l.State.Slot(), l.Block)
+			header, err := lightClient.BlockToLightClientHeader(
+				l.Ctx,
+				primitives.Slot(params.BeaconConfig().DenebForkEpoch)*params.BeaconConfig().SlotsPerEpoch,
+				l.Block,
+			)
 			require.NoError(t, err)
 			require.NotNil(t, header, "header is nil")
 
@@ -577,7 +599,11 @@ func TestLightClient_BlockToLightClientHeader(t *testing.T) {
 		t.Run("Blinded Beacon Block", func(t *testing.T) {
 			l := util.NewTestLightClient(t).SetupTestDeneb(true)
 
-			header, err := lightClient.BlockToLightClientHeader(l.Ctx, l.State.Slot(), l.Block)
+			header, err := lightClient.BlockToLightClientHeader(
+				l.Ctx,
+				primitives.Slot(params.BeaconConfig().DenebForkEpoch)*params.BeaconConfig().SlotsPerEpoch,
+				l.Block,
+			)
 			require.NoError(t, err)
 			require.NotNil(t, header, "header is nil")
 
@@ -771,6 +797,172 @@ func TestLightClient_BlockToLightClientHeader(t *testing.T) {
 			require.DeepSSZEqual(t, executionPayloadProof, convertArrayToSlice(headerExecutionBranch), "Execution payload proofs are not equal")
 		})
 	})
+
+	t.Run("Capella fork with Altair block", func(t *testing.T) {
+		l := util.NewTestLightClient(t).SetupTestAltair()
+
+		header, err := lightClient.BlockToLightClientHeader(
+			l.Ctx,
+			primitives.Slot(params.BeaconConfig().CapellaForkEpoch)*params.BeaconConfig().SlotsPerEpoch,
+			l.Block)
+		require.NoError(t, err)
+		require.NotNil(t, header, "header is nil")
+
+		parentRoot := l.Block.Block().ParentRoot()
+		stateRoot := l.Block.Block().StateRoot()
+		bodyRoot, err := l.Block.Block().Body().HashTreeRoot()
+		require.NoError(t, err)
+
+		require.Equal(t, l.Block.Block().Slot(), header.Beacon().Slot, "Slot is not equal")
+		require.Equal(t, l.Block.Block().ProposerIndex(), header.Beacon().ProposerIndex, "Proposer index is not equal")
+		require.DeepSSZEqual(t, parentRoot[:], header.Beacon().ParentRoot, "Parent root is not equal")
+		require.DeepSSZEqual(t, stateRoot[:], header.Beacon().StateRoot, "State root is not equal")
+		require.DeepSSZEqual(t, bodyRoot[:], header.Beacon().BodyRoot, "Body root is not equal")
+	})
+
+	t.Run("Deneb fork with Altair block", func(t *testing.T) {
+		l := util.NewTestLightClient(t).SetupTestAltair()
+
+		header, err := lightClient.BlockToLightClientHeader(
+			l.Ctx,
+			primitives.Slot(params.BeaconConfig().DenebForkEpoch)*params.BeaconConfig().SlotsPerEpoch,
+			l.Block)
+		require.NoError(t, err)
+		require.NotNil(t, header, "header is nil")
+
+		parentRoot := l.Block.Block().ParentRoot()
+		stateRoot := l.Block.Block().StateRoot()
+		bodyRoot, err := l.Block.Block().Body().HashTreeRoot()
+		require.NoError(t, err)
+
+		require.Equal(t, l.Block.Block().Slot(), header.Beacon().Slot, "Slot is not equal")
+		require.Equal(t, l.Block.Block().ProposerIndex(), header.Beacon().ProposerIndex, "Proposer index is not equal")
+		require.DeepSSZEqual(t, parentRoot[:], header.Beacon().ParentRoot, "Parent root is not equal")
+		require.DeepSSZEqual(t, stateRoot[:], header.Beacon().StateRoot, "State root is not equal")
+		require.DeepSSZEqual(t, bodyRoot[:], header.Beacon().BodyRoot, "Body root is not equal")
+	})
+
+	t.Run("Deneb fork with Capella block", func(t *testing.T) {
+		t.Run("Non-Blinded Beacon Block", func(t *testing.T) {
+			l := util.NewTestLightClient(t).SetupTestCapella(false)
+
+			header, err := lightClient.BlockToLightClientHeader(
+				l.Ctx,
+				primitives.Slot(params.BeaconConfig().DenebForkEpoch)*params.BeaconConfig().SlotsPerEpoch,
+				l.Block)
+			require.NoError(t, err)
+			require.NotNil(t, header, "header is nil")
+
+			parentRoot := l.Block.Block().ParentRoot()
+			stateRoot := l.Block.Block().StateRoot()
+			bodyRoot, err := l.Block.Block().Body().HashTreeRoot()
+			require.NoError(t, err)
+
+			payload, err := l.Block.Block().Body().Execution()
+			require.NoError(t, err)
+
+			transactionsRoot, err := lightClient.ComputeTransactionsRoot(payload)
+			require.NoError(t, err)
+
+			withdrawalsRoot, err := lightClient.ComputeWithdrawalsRoot(payload)
+			require.NoError(t, err)
+
+			executionHeader := &v11.ExecutionPayloadHeaderDeneb{
+				ParentHash:       payload.ParentHash(),
+				FeeRecipient:     payload.FeeRecipient(),
+				StateRoot:        payload.StateRoot(),
+				ReceiptsRoot:     payload.ReceiptsRoot(),
+				LogsBloom:        payload.LogsBloom(),
+				PrevRandao:       payload.PrevRandao(),
+				BlockNumber:      payload.BlockNumber(),
+				GasLimit:         payload.GasLimit(),
+				GasUsed:          payload.GasUsed(),
+				Timestamp:        payload.Timestamp(),
+				ExtraData:        payload.ExtraData(),
+				BaseFeePerGas:    payload.BaseFeePerGas(),
+				BlockHash:        payload.BlockHash(),
+				TransactionsRoot: transactionsRoot,
+				WithdrawalsRoot:  withdrawalsRoot,
+			}
+
+			executionPayloadProof, err := blocks.PayloadProof(l.Ctx, l.Block.Block())
+			require.NoError(t, err)
+
+			require.Equal(t, l.Block.Block().Slot(), header.Beacon().Slot, "Slot is not equal")
+			require.Equal(t, l.Block.Block().ProposerIndex(), header.Beacon().ProposerIndex, "Proposer index is not equal")
+			require.DeepSSZEqual(t, parentRoot[:], header.Beacon().ParentRoot, "Parent root is not equal")
+			require.DeepSSZEqual(t, stateRoot[:], header.Beacon().StateRoot, "State root is not equal")
+			require.DeepSSZEqual(t, bodyRoot[:], header.Beacon().BodyRoot, "Body root is not equal")
+
+			headerExecution, err := header.Execution()
+			require.NoError(t, err)
+			require.DeepSSZEqual(t, executionHeader, headerExecution.Proto(), "Execution headers are not equal")
+
+			headerExecutionBranch, err := header.ExecutionBranch()
+			require.NoError(t, err)
+			require.DeepSSZEqual(t, executionPayloadProof, convertArrayToSlice(headerExecutionBranch), "Execution payload proofs are not equal")
+		})
+
+		t.Run("Blinded Beacon Block", func(t *testing.T) {
+			l := util.NewTestLightClient(t).SetupTestCapella(true)
+
+			header, err := lightClient.BlockToLightClientHeader(
+				l.Ctx,
+				primitives.Slot(params.BeaconConfig().DenebForkEpoch)*params.BeaconConfig().SlotsPerEpoch,
+				l.Block)
+			require.NoError(t, err)
+			require.NotNil(t, header, "header is nil")
+
+			parentRoot := l.Block.Block().ParentRoot()
+			stateRoot := l.Block.Block().StateRoot()
+			bodyRoot, err := l.Block.Block().Body().HashTreeRoot()
+			require.NoError(t, err)
+
+			payload, err := l.Block.Block().Body().Execution()
+			require.NoError(t, err)
+
+			transactionsRoot, err := payload.TransactionsRoot()
+			require.NoError(t, err)
+
+			withdrawalsRoot, err := payload.WithdrawalsRoot()
+			require.NoError(t, err)
+
+			executionHeader := &v11.ExecutionPayloadHeaderDeneb{
+				ParentHash:       payload.ParentHash(),
+				FeeRecipient:     payload.FeeRecipient(),
+				StateRoot:        payload.StateRoot(),
+				ReceiptsRoot:     payload.ReceiptsRoot(),
+				LogsBloom:        payload.LogsBloom(),
+				PrevRandao:       payload.PrevRandao(),
+				BlockNumber:      payload.BlockNumber(),
+				GasLimit:         payload.GasLimit(),
+				GasUsed:          payload.GasUsed(),
+				Timestamp:        payload.Timestamp(),
+				ExtraData:        payload.ExtraData(),
+				BaseFeePerGas:    payload.BaseFeePerGas(),
+				BlockHash:        payload.BlockHash(),
+				TransactionsRoot: transactionsRoot,
+				WithdrawalsRoot:  withdrawalsRoot,
+			}
+
+			executionPayloadProof, err := blocks.PayloadProof(l.Ctx, l.Block.Block())
+			require.NoError(t, err)
+
+			require.Equal(t, l.Block.Block().Slot(), header.Beacon().Slot, "Slot is not equal")
+			require.Equal(t, l.Block.Block().ProposerIndex(), header.Beacon().ProposerIndex, "Proposer index is not equal")
+			require.DeepSSZEqual(t, parentRoot[:], header.Beacon().ParentRoot, "Parent root is not equal")
+			require.DeepSSZEqual(t, stateRoot[:], header.Beacon().StateRoot, "State root is not equal")
+			require.DeepSSZEqual(t, bodyRoot[:], header.Beacon().BodyRoot, "Body root is not equal")
+
+			headerExecution, err := header.Execution()
+			require.NoError(t, err)
+			require.DeepSSZEqual(t, executionHeader, headerExecution.Proto(), "Execution headers are not equal")
+
+			headerExecutionBranch, err := header.ExecutionBranch()
+			require.NoError(t, err)
+			require.DeepSSZEqual(t, executionPayloadProof, convertArrayToSlice(headerExecutionBranch), "Execution payload proofs are not equal")
+		})
+	})
 }
 
 func convertArrayToSlice(arr [4][32]uint8) [][]uint8 {

consensus-types/light-client/bootstrap.go

@@ -90,7 +90,7 @@ func (h *bootstrapAltair) Header() interfaces.LightClientHeader {
 func (h *bootstrapAltair) SetHeader(header interfaces.LightClientHeader) error {
 	p, ok := (header.Proto()).(*pb.LightClientHeaderAltair)
 	if !ok {
-		return fmt.Errorf("header type %T is not %T", p, &pb.LightClientHeaderAltair{})
+		return fmt.Errorf("header type %T is not %T", header.Proto(), &pb.LightClientHeaderAltair{})
 	}
 	h.p.Header = p
 	h.header = header
@@ -188,7 +188,7 @@ func (h *bootstrapCapella) Header() interfaces.LightClientHeader {
 func (h *bootstrapCapella) SetHeader(header interfaces.LightClientHeader) error {
 	p, ok := (header.Proto()).(*pb.LightClientHeaderCapella)
 	if !ok {
-		return fmt.Errorf("header type %T is not %T", p, &pb.LightClientHeaderCapella{})
+		return fmt.Errorf("header type %T is not %T", header.Proto(), &pb.LightClientHeaderCapella{})
 	}
 	h.p.Header = p
 	h.header = header
@@ -286,7 +286,7 @@ func (h *bootstrapDeneb) Header() interfaces.LightClientHeader {
 func (h *bootstrapDeneb) SetHeader(header interfaces.LightClientHeader) error {
 	p, ok := (header.Proto()).(*pb.LightClientHeaderDeneb)
 	if !ok {
-		return fmt.Errorf("header type %T is not %T", p, &pb.LightClientHeaderDeneb{})
+		return fmt.Errorf("header type %T is not %T", header.Proto(), &pb.LightClientHeaderDeneb{})
 	}
 	h.p.Header = p
 	h.header = header
@@ -384,7 +384,7 @@ func (h *bootstrapElectra) Header() interfaces.LightClientHeader {
 func (h *bootstrapElectra) SetHeader(header interfaces.LightClientHeader) error {
 	p, ok := (header.Proto()).(*pb.LightClientHeaderDeneb)
 	if !ok {
-		return fmt.Errorf("header type %T is not %T", p, &pb.LightClientHeaderDeneb{})
+		return fmt.Errorf("header type %T is not %T", header.Proto(), &pb.LightClientHeaderDeneb{})
 	}
 	h.p.Header = p
 	h.header = header

consensus-types/light-client/update.go

@@ -115,7 +115,7 @@ func (u *updateAltair) AttestedHeader() interfaces.LightClientHeader {
 func (u *updateAltair) SetAttestedHeader(header interfaces.LightClientHeader) error {
 	proto, ok := header.Proto().(*pb.LightClientHeaderAltair)
 	if !ok {
-		return fmt.Errorf("header type %T is not %T", proto, &pb.LightClientHeaderAltair{})
+		return fmt.Errorf("header type %T is not %T", header.Proto(), &pb.LightClientHeaderAltair{})
 	}
 	u.p.AttestedHeader = proto
 	u.attestedHeader = header
@@ -157,7 +157,7 @@ func (u *updateAltair) FinalizedHeader() interfaces.LightClientHeader {
 func (u *updateAltair) SetFinalizedHeader(header interfaces.LightClientHeader) error {
 	proto, ok := header.Proto().(*pb.LightClientHeaderAltair)
 	if !ok {
-		return fmt.Errorf("header type %T is not %T", proto, &pb.LightClientHeaderAltair{})
+		return fmt.Errorf("header type %T is not %T", header.Proto(), &pb.LightClientHeaderAltair{})
 	}
 	u.p.FinalizedHeader = proto
 	u.finalizedHeader = header
@@ -282,7 +282,7 @@ func (u *updateCapella) AttestedHeader() interfaces.LightClientHeader {
 func (u *updateCapella) SetAttestedHeader(header interfaces.LightClientHeader) error {
 	proto, ok := header.Proto().(*pb.LightClientHeaderCapella)
 	if !ok {
-		return fmt.Errorf("header type %T is not %T", proto, &pb.LightClientHeaderCapella{})
+		return fmt.Errorf("header type %T is not %T", header.Proto(), &pb.LightClientHeaderCapella{})
 	}
 	u.p.AttestedHeader = proto
 	u.attestedHeader = header
@@ -324,7 +324,7 @@ func (u *updateCapella) FinalizedHeader() interfaces.LightClientHeader {
 func (u *updateCapella) SetFinalizedHeader(header interfaces.LightClientHeader) error {
 	proto, ok := header.Proto().(*pb.LightClientHeaderCapella)
 	if !ok {
-		return fmt.Errorf("header type %T is not %T", proto, &pb.LightClientHeaderCapella{})
+		return fmt.Errorf("header type %T is not %T", header.Proto(), &pb.LightClientHeaderCapella{})
 	}
 	u.p.FinalizedHeader = proto
 	u.finalizedHeader = header
@@ -449,7 +449,7 @@ func (u *updateDeneb) AttestedHeader() interfaces.LightClientHeader {
 func (u *updateDeneb) SetAttestedHeader(header interfaces.LightClientHeader) error {
 	proto, ok := header.Proto().(*pb.LightClientHeaderDeneb)
 	if !ok {
-		return fmt.Errorf("header type %T is not %T", proto, &pb.LightClientHeaderDeneb{})
+		return fmt.Errorf("header type %T is not %T", header.Proto(), &pb.LightClientHeaderDeneb{})
 	}
 	u.p.AttestedHeader = proto
 	u.attestedHeader = header
@@ -491,7 +491,7 @@ func (u *updateDeneb) FinalizedHeader() interfaces.LightClientHeader {
 func (u *updateDeneb) SetFinalizedHeader(header interfaces.LightClientHeader) error {
 	proto, ok := header.Proto().(*pb.LightClientHeaderDeneb)
 	if !ok {
-		return fmt.Errorf("header type %T is not %T", proto, &pb.LightClientHeaderDeneb{})
+		return fmt.Errorf("header type %T is not %T", header.Proto(), &pb.LightClientHeaderDeneb{})
 	}
 	u.p.FinalizedHeader = proto
 	u.finalizedHeader = header
@@ -617,7 +617,7 @@ func (u *updateElectra) AttestedHeader() interfaces.LightClientHeader {
 func (u *updateElectra) SetAttestedHeader(header interfaces.LightClientHeader) error {
 	proto, ok := header.Proto().(*pb.LightClientHeaderDeneb)
 	if !ok {
-		return fmt.Errorf("header type %T is not %T", proto, &pb.LightClientHeaderDeneb{})
+		return fmt.Errorf("header type %T is not %T", header.Proto(), &pb.LightClientHeaderDeneb{})
 	}
 	u.p.AttestedHeader = proto
 	u.attestedHeader = header
@@ -659,7 +659,7 @@ func (u *updateElectra) FinalizedHeader() interfaces.LightClientHeader {
 func (u *updateElectra) SetFinalizedHeader(header interfaces.LightClientHeader) error {
 	proto, ok := header.Proto().(*pb.LightClientHeaderDeneb)
 	if !ok {
-		return fmt.Errorf("header type %T is not %T", proto, &pb.LightClientHeaderDeneb{})
+		return fmt.Errorf("header type %T is not %T", header.Proto(), &pb.LightClientHeaderDeneb{})
 	}
 	u.p.FinalizedHeader = proto
 	u.finalizedHeader = header