diff --git a/chain/consensus/filcns/filecoin.go b/chain/consensus/filcns/filecoin.go
index 9f16c7d99..c163c9c3b 100644
--- a/chain/consensus/filcns/filecoin.go
+++ b/chain/consensus/filcns/filecoin.go
@@ -577,15 +577,8 @@ func (filec *FilecoinEC) checkBlockMessages(ctx context.Context, b *types.FullBl
 
 	smArr := blockadt.MakeEmptyArray(tmpstore)
 	for i, m := range b.SecpkMessages {
-		switch nv := filec.sm.GetNetworkVersion(ctx, b.Header.Height); {
-		case nv >= network.Version14 && nv < network.Version18:
-			if typ := m.Signature.Type; typ != crypto.SigTypeSecp256k1 {
-				return xerrors.Errorf("block had invalid secpk message at index %d: %w", i, err)
-			}
-		case nv >= network.Version18:
-			if typ := m.Signature.Type; typ != crypto.SigTypeSecp256k1 && typ != crypto.SigTypeDelegated {
-				return xerrors.Errorf("block had invalid signed message at index %d: %w", i, err)
-			}
+		if !filec.ValidateSecpkSigType(nv, m.Signature.Type) {
+			return xerrors.Errorf("block had invalid signed message at index %d: %w", i, err)
 		}
 
 		if err := checkMsg(m); err != nil {
@@ -908,4 +901,17 @@ func (filec *FilecoinEC) isChainNearSynced() bool {
 	return build.Clock.Since(timestampTime) < 6*time.Hour
 }
 
+// ValidateSecpkSigType checks that a signature type is valid for the network
+// version, for a "secpk" message.
+func (filec *FilecoinEC) ValidateSecpkSigType(nv network.Version, typ crypto.SigType) bool {
+	switch {
+	case nv < network.Version14:
+		return true // no check for signature type before nv14
+	case nv >= network.Version14 && nv < network.Version18:
+		return typ == crypto.SigTypeSecp256k1
+	default:
+		return typ == crypto.SigTypeSecp256k1 || typ == crypto.SigTypeDelegated
+	}
+}
+
 var _ consensus.Consensus = &FilecoinEC{}