diff --git a/builder/beacon_client_test.go b/builder/beacon_client_test.go
index 152e891c892a..564275e5ad89 100644
--- a/builder/beacon_client_test.go
+++ b/builder/beacon_client_test.go
@@ -212,10 +212,10 @@ func TestOnForkchoiceUpdate(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, PubkeyHex("0x93247f2209abcacf57b75a51dafae777f9dd38bc7053d1af526f220a7489a6d3a2753e5f3e8b1cfe39b56f43611df74b"), pubkeyHex)
 
-	pubkeyHex, err = bc.getProposerForNextSlot(31)
+	_, err = bc.getProposerForNextSlot(31)
 	require.EqualError(t, err, "slot out of sync")
 
-	pubkeyHex, err = bc.getProposerForNextSlot(33)
+	_, err = bc.getProposerForNextSlot(33)
 	require.EqualError(t, err, "slot out of sync")
 
 	mbn.headersCode = 404
@@ -263,6 +263,6 @@ func TestOnForkchoiceUpdate(t *testing.T) {
 
 	// Check proposers map error is routed out
 	mbn.headersResp = []byte(`{ "data": [ { "header": { "message": { "slot": "65", "proposer_index": "1" } } } ] }`)
-	slot, err = bc.onForkchoiceUpdate()
+	_, err = bc.onForkchoiceUpdate()
 	require.EqualError(t, err, "inconsistent proposer mapping")
 }
diff --git a/builder/service.go b/builder/service.go
index d7da282ad261..f934d5e31c79 100644
--- a/builder/service.go
+++ b/builder/service.go
@@ -2,6 +2,7 @@ package builder
 
 import (
 	"errors"
+	"fmt"
 	"net/http"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -97,12 +98,20 @@ func Register(stack *node.Node, backend *eth.Ethereum, cfg *BuilderConfig) error
 	}
 
 	genesisForkVersionBytes, err := hexutil.Decode(cfg.GenesisForkVersion)
+	if err != nil {
+		return fmt.Errorf("invalid genesisForkVersion: %w", err)
+	}
+
 	var genesisForkVersion [4]byte
 	copy(genesisForkVersion[:], genesisForkVersionBytes[:4])
 	builderSigningDomain := boostTypes.ComputeDomain(boostTypes.DomainTypeAppBuilder, genesisForkVersion, boostTypes.Root{})
 
 	genesisValidatorsRoot := boostTypes.Root(common.HexToHash(cfg.GenesisValidatorsRoot))
 	bellatrixForkVersionBytes, err := hexutil.Decode(cfg.BellatrixForkVersion)
+	if err != nil {
+		return fmt.Errorf("invalid bellatrixForkVersion: %w", err)
+	}
+
 	var bellatrixForkVersion [4]byte
 	copy(bellatrixForkVersion[:], bellatrixForkVersionBytes[:4])
 	proposerSigningDomain := boostTypes.ComputeDomain(boostTypes.DomainTypeBeaconProposer, bellatrixForkVersion, genesisValidatorsRoot)
diff --git a/builder/validator.go b/builder/validator.go
index b1554a4f9595..2a27d44b9248 100644
--- a/builder/validator.go
+++ b/builder/validator.go
@@ -45,5 +45,5 @@ func (v *ValidatorPrivateData) PrepareRegistrationMessage(feeRecipientHex string
 	if err != nil {
 		return boostTypes.SignedValidatorRegistration{}, err
 	}
-	return boostTypes.SignedValidatorRegistration{msg, signature}, nil
+	return boostTypes.SignedValidatorRegistration{Message: msg, Signature: signature}, nil
 }