diff --git a/privval/file.go b/privval/file.go
index cefbef376..a0835cfeb 100644
--- a/privval/file.go
+++ b/privval/file.go
@@ -405,10 +405,11 @@ func (pv *FilePV) signVote(chainID string, vote *tmproto.Vote) error {
 	vote.Signature = sig
 
 	// Sign the vote extension, regardless of whether it's present or not
-	vote.ExtensionSignature, err = pv.Key.PrivKey.Sign(extSignBytes)
+	extSig, err := pv.Key.PrivKey.Sign(extSignBytes)
 	if err != nil {
 		return err
 	}
+	vote.ExtensionSignature = extSig
 
 	return nil
 }
diff --git a/types/priv_validator.go b/types/priv_validator.go
index cbf3896fd..29620f829 100644
--- a/types/priv_validator.go
+++ b/types/priv_validator.go
@@ -96,8 +96,12 @@ func (pv MockPV) SignVote(ctx context.Context, chainID string, vote *tmproto.Vot
 		return err
 	}
 	vote.Signature = sig
-	vote.ExtensionSignature, err = pv.PrivKey.Sign(extSignBytes)
-	return err
+	extSig, err := pv.PrivKey.Sign(extSignBytes)
+	if err != nil {
+		return err
+	}
+	vote.ExtensionSignature = extSig
+	return nil
 }
 
 // Implements PrivValidator.