diff --git a/ethutil/rlp.go b/ethutil/rlp.go
index e633f5f1dc..33ec0d3598 100644
--- a/ethutil/rlp.go
+++ b/ethutil/rlp.go
@@ -9,6 +9,10 @@ import (
 	"math/big"
 )
 
+type RlpEncodable interface {
+	RlpEncode() []byte
+}
+
 type RlpEncoder struct {
 	rlpData []byte
 }