diff --git a/rvgo/fast/evm.go b/rvgo/fast/evm.go
index 696a0fc1..f90ed3d5 100644
--- a/rvgo/fast/evm.go
+++ b/rvgo/fast/evm.go
@@ -3,7 +3,7 @@ package fast
 import "github.com/ethereum/go-ethereum/crypto"
 
 var (
-	StepBytes4                      = crypto.Keccak256([]byte("step(bytes,bytes)"))[:4]
+	StepBytes4                      = crypto.Keccak256([]byte("step(bytes,bytes,bytes32)"))[:4]
 	CheatBytes4                     = crypto.Keccak256([]byte("cheat(uint256,bytes32,bytes32,uint256)"))[:4]
 	LoadKeccak256PreimagePartBytes4 = crypto.Keccak256([]byte("loadKeccak256PreimagePart(uint256,bytes)"))[:4]
 )
diff --git a/rvgo/fast/witness.go b/rvgo/fast/witness.go
index 549005b8..9b6538c7 100644
--- a/rvgo/fast/witness.go
+++ b/rvgo/fast/witness.go
@@ -5,9 +5,12 @@ import (
 	"errors"
 	"fmt"
 
-	"github.com/ethereum-optimism/optimism/op-preimage"
+	preimage "github.com/ethereum-optimism/optimism/op-preimage"
+	"github.com/ethereum/go-ethereum/common"
 )
 
+type LocalContext common.Hash
+
 type StepWitness struct {
 	// encoded state witness
 	State []byte
@@ -27,19 +30,25 @@ func uint64ToBytes32(v uint64) []byte {
 
 func (wit *StepWitness) EncodeStepInput() []byte {
 	abiStatePadding := (32 - (uint64(len(wit.State)) % 32)) % 32
+	abiProofPadding := (32 - (uint64(len(wit.MemProof)) % 32)) % 32
 
 	var input []byte
 	input = append(input, StepBytes4...)
-	input = append(input, uint64ToBytes32(32*2)...)                                           // state data offset in bytes
-	input = append(input, uint64ToBytes32(32*2+32+uint64(len(wit.State))+abiStatePadding)...) // proof data offset in bytes
-	// TODO pad state data to multiple of 32 bytes
-	// TODO also pad proof data
-
-	input = append(input, uint64ToBytes32(uint64(len(wit.State)))...) // state data length in bytes
+	// state data offset in bytes
+	input = append(input, uint64ToBytes32(32*3)...)
+	// proof data offset in bytes
+	input = append(input, uint64ToBytes32(32*3+32+uint64(len(wit.State))+abiStatePadding)...)
+	// dummy localContext
+	input = append(input, make([]byte, 32)...)
+	
+	// state data length in bytes
+	input = append(input, uint64ToBytes32(uint64(len(wit.State)))...)
 	input = append(input, wit.State[:]...)
 	input = append(input, make([]byte, abiStatePadding)...)
-	input = append(input, uint64ToBytes32(uint64(len(wit.MemProof)))...) // proof data length in bytes
+	// proof data length in bytes
+	input = append(input, uint64ToBytes32(uint64(len(wit.MemProof)))...)
 	input = append(input, wit.MemProof[:]...)
+	input = append(input, make([]byte, abiProofPadding)...)
 	return input
 }