diff --git a/validator/client/validator_aggregate.go b/validator/client/validator_aggregate.go
index c83140b995d8..c90ce75cb395 100644
--- a/validator/client/validator_aggregate.go
+++ b/validator/client/validator_aggregate.go
@@ -96,21 +96,14 @@ func (v *validator) SubmitAggregateAndProof(ctx context.Context, slot uint64, pu
 		return
 	}
 
-	d, err := v.domainData(ctx, helpers.SlotToEpoch(res.AggregateAndProof.Aggregate.Data.Slot), params.BeaconConfig().DomainAggregateAndProof[:])
+	sig, err := v.aggregateAndProofSig(ctx, pubKey, res.AggregateAndProof)
 	if err != nil {
-		log.Errorf("Could not get domain data to sign aggregate and proof: %v", err)
-		return
+		log.Errorf("Could not sign aggregate and proof: %v", err)
 	}
-	signedRoot, err := helpers.ComputeSigningRoot(res.AggregateAndProof, d.SignatureDomain)
-	if err != nil {
-		log.Errorf("Could not compute sign root for aggregate and proof: %v", err)
-		return
-	}
-
 	_, err = v.validatorClient.SubmitSignedAggregateSelectionProof(ctx, &ethpb.SignedAggregateSubmitRequest{
 		SignedAggregateAndProof: &ethpb.SignedAggregateAttestationAndProof{
 			Message:   res.AggregateAndProof,
-			Signature: signedRoot[:],
+			Signature: sig,
 		},
 	})
 	if err != nil {
@@ -165,6 +158,25 @@ func (v *validator) waitToSlotTwoThirds(ctx context.Context, slot uint64) {
 	time.Sleep(roughtime.Until(finalTime))
 }
 
+// This returns the signature of validator signing over aggregate and
+// proof object.
+func (v *validator) aggregateAndProofSig(ctx context.Context, pubKey [48]byte, agg *ethpb.AggregateAttestationAndProof) ([]byte, error) {
+	d, err := v.domainData(ctx, helpers.SlotToEpoch(agg.Aggregate.Data.Slot), params.BeaconConfig().DomainAggregateAndProof[:])
+	if err != nil {
+		return nil, err
+	}
+	signedRoot, err := helpers.ComputeSigningRoot(agg, d.SignatureDomain)
+	if err != nil {
+		return nil, err
+	}
+	sig, err := v.keyManager.Sign(pubKey, signedRoot)
+	if err != nil {
+		return nil, err
+	}
+
+	return sig.Marshal(), nil
+}
+
 func (v *validator) addIndicesToLog(duty *ethpb.DutiesResponse_Duty) error {
 	v.attLogsLock.Lock()
 	defer v.attLogsLock.Unlock()
diff --git a/validator/client/validator_aggregate_test.go b/validator/client/validator_aggregate_test.go
index 9a33eb3e9887..d9707aebb6e9 100644
--- a/validator/client/validator_aggregate_test.go
+++ b/validator/client/validator_aggregate_test.go
@@ -6,6 +6,7 @@ import (
 
 	"github.com/golang/mock/gomock"
 	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
+	"github.com/prysmaticlabs/prysm/shared/bls"
 	"github.com/prysmaticlabs/prysm/shared/params"
 	"github.com/prysmaticlabs/prysm/shared/roughtime"
 	"github.com/prysmaticlabs/prysm/shared/testutil"
@@ -78,3 +79,26 @@ func TestWaitForSlotTwoThird_WaitCorrectly(t *testing.T) {
 		t.Errorf("Wanted %d time for slot two third but got %d", twoThirdTime, currentTime)
 	}
 }
+
+func TestAggregateAndProofSignature_CanSignValidSignature(t *testing.T) {
+	validator, m, finish := setup(t)
+	defer finish()
+
+	m.validatorClient.EXPECT().DomainData(
+		gomock.Any(), // ctx
+		&ethpb.DomainRequest{Epoch: 0, Domain: params.BeaconConfig().DomainAggregateAndProof[:]},
+	).Return(&ethpb.DomainResponse{}, nil /*err*/)
+
+	agg := &ethpb.AggregateAttestationAndProof{
+		AggregatorIndex: 0,
+		Aggregate:       &ethpb.Attestation{Data: &ethpb.AttestationData{}},
+		SelectionProof:  nil,
+	}
+	sig, err := validator.aggregateAndProofSig(context.Background(), validatorPubKey, agg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := bls.SignatureFromBytes(sig); err != nil {
+		t.Fatal(err)
+	}
+}