diff --git a/pub_key.go b/pub_key.go
index 47eba9ed6..c5d3cadc2 100644
--- a/pub_key.go
+++ b/pub_key.go
@@ -13,6 +13,7 @@ import (
 // PubKey is part of Account and Validator.
 type PubKey interface {
 	Address() []byte
+	KeyString() string
 	VerifyBytes(msg []byte, sig Signature) bool
 }
 
diff --git a/signature_test.go b/signature_test.go
index 1dbc58096..b7eec577f 100644
--- a/signature_test.go
+++ b/signature_test.go
@@ -42,7 +42,7 @@ func TestBinaryDecode(t *testing.T) {
 	sig := privKey.Sign(msg)
 	t.Logf("msg: %X, sig: %X", msg, sig)
 
-	buf, n, err := new(bytes.Buffer), new(int64), new(error)
+	buf, n, err := new(bytes.Buffer), new(int), new(error)
 	wire.WriteBinary(sig, buf, n, err)
 	if *err != nil {
 		t.Fatalf("Failed to write Signature: %v", err)
@@ -56,7 +56,7 @@ func TestBinaryDecode(t *testing.T) {
 		t.Fatalf("Unexpected signature type byte")
 	}
 
-	sig2, ok := wire.ReadBinary(SignatureEd25519{}, buf, n, err).(SignatureEd25519)
+	sig2, ok := wire.ReadBinary(SignatureEd25519{}, buf, 0, n, err).(SignatureEd25519)
 	if !ok || *err != nil {
 		t.Fatalf("Failed to read Signature: %v", err)
 	}