diff --git a/opcode.go b/opcode.go
index 2ef4444e..80d83aee 100644
--- a/opcode.go
+++ b/opcode.go
@@ -11,6 +11,7 @@ import (
 	"crypto/sha1"
 	"crypto/sha256"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"github.com/conformal/btcec"
 	"github.com/conformal/btcwire"