diff --git a/ethclient/ethclient.go b/ethclient/ethclient.go
index f89f39a3bf..b73cc2d7d2 100644
--- a/ethclient/ethclient.go
+++ b/ethclient/ethclient.go
@@ -853,13 +853,21 @@ func (s SimulateBlock) MarshalJSON() ([]byte, error) {
 	})
 }
 
+//go:generate go run github.com/fjl/gencodec -type SimulateCallResult -field-override simulateCallResultMarshaling -out gen_simulate_call_result.go
+
 // SimulateCallResult is the result of a simulated call.
 type SimulateCallResult struct {
-	ReturnValue hexutil.Bytes  `json:"returnData"`
-	Logs        []*types.Log   `json:"logs"`
-	GasUsed     hexutil.Uint64 `json:"gasUsed"`
-	Status      hexutil.Uint64 `json:"status"`
-	Error       *CallError     `json:"error,omitempty"`
+	ReturnValue []byte       `json:"returnData"`
+	Logs        []*types.Log `json:"logs"`
+	GasUsed     uint64       `json:"gasUsed"`
+	Status      uint64       `json:"status"`
+	Error       *CallError   `json:"error,omitempty"`
+}
+
+type simulateCallResultMarshaling struct {
+	ReturnValue hexutil.Bytes
+	GasUsed     hexutil.Uint64
+	Status      hexutil.Uint64
 }
 
 // CallError represents an error from a simulated call.
@@ -869,18 +877,28 @@ type CallError struct {
 	Data    string `json:"data,omitempty"`
 }
 
+//go:generate go run github.com/fjl/gencodec -type SimulateBlockResult -field-override simulateBlockResultMarshaling -out gen_simulate_block_result.go
+
 // SimulateBlockResult represents the result of a simulated block.
 type SimulateBlockResult struct {
-	Number        hexutil.Uint64       `json:"number"`
+	Number        uint64               `json:"number"`
 	Hash          common.Hash          `json:"hash"`
-	Timestamp     hexutil.Uint64       `json:"timestamp"`
-	GasLimit      hexutil.Uint64       `json:"gasLimit"`
-	GasUsed       hexutil.Uint64       `json:"gasUsed"`
+	Timestamp     uint64               `json:"timestamp"`
+	GasLimit      uint64               `json:"gasLimit"`
+	GasUsed       uint64               `json:"gasUsed"`
 	FeeRecipient  common.Address       `json:"miner"`
-	BaseFeePerGas *hexutil.Big         `json:"baseFeePerGas,omitempty"`
+	BaseFeePerGas *big.Int             `json:"baseFeePerGas,omitempty"`
 	Calls         []SimulateCallResult `json:"calls"`
 }
 
+type simulateBlockResultMarshaling struct {
+	Number        hexutil.Uint64
+	Timestamp     hexutil.Uint64
+	GasLimit      hexutil.Uint64
+	GasUsed       hexutil.Uint64
+	BaseFeePerGas *hexutil.Big
+}
+
 // SimulateV1 executes transactions on top of a base state.
 func (ec *Client) SimulateV1(ctx context.Context, opts SimulateOptions, blockNrOrHash *rpc.BlockNumberOrHash) ([]SimulateBlockResult, error) {
 	var result []SimulateBlockResult
diff --git a/ethclient/gen_simulate_block_result.go b/ethclient/gen_simulate_block_result.go
new file mode 100644
index 0000000000..d3f712d102
--- /dev/null
+++ b/ethclient/gen_simulate_block_result.go
@@ -0,0 +1,80 @@
+// Code generated by github.com/fjl/gencodec. DO NOT EDIT.
+
+package ethclient
+
+import (
+	"encoding/json"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+)
+
+var _ = (*simulateBlockResultMarshaling)(nil)
+
+// MarshalJSON marshals as JSON.
+func (s SimulateBlockResult) MarshalJSON() ([]byte, error) {
+	type SimulateBlockResult struct {
+		Number        hexutil.Uint64       `json:"number"`
+		Hash          common.Hash          `json:"hash"`
+		Timestamp     hexutil.Uint64       `json:"timestamp"`
+		GasLimit      hexutil.Uint64       `json:"gasLimit"`
+		GasUsed       hexutil.Uint64       `json:"gasUsed"`
+		FeeRecipient  common.Address       `json:"miner"`
+		BaseFeePerGas *hexutil.Big         `json:"baseFeePerGas,omitempty"`
+		Calls         []SimulateCallResult `json:"calls"`
+	}
+	var enc SimulateBlockResult
+	enc.Number = hexutil.Uint64(s.Number)
+	enc.Hash = s.Hash
+	enc.Timestamp = hexutil.Uint64(s.Timestamp)
+	enc.GasLimit = hexutil.Uint64(s.GasLimit)
+	enc.GasUsed = hexutil.Uint64(s.GasUsed)
+	enc.FeeRecipient = s.FeeRecipient
+	enc.BaseFeePerGas = (*hexutil.Big)(s.BaseFeePerGas)
+	enc.Calls = s.Calls
+	return json.Marshal(&enc)
+}
+
+// UnmarshalJSON unmarshals from JSON.
+func (s *SimulateBlockResult) UnmarshalJSON(input []byte) error {
+	type SimulateBlockResult struct {
+		Number        *hexutil.Uint64      `json:"number"`
+		Hash          *common.Hash         `json:"hash"`
+		Timestamp     *hexutil.Uint64      `json:"timestamp"`
+		GasLimit      *hexutil.Uint64      `json:"gasLimit"`
+		GasUsed       *hexutil.Uint64      `json:"gasUsed"`
+		FeeRecipient  *common.Address      `json:"miner"`
+		BaseFeePerGas *hexutil.Big         `json:"baseFeePerGas,omitempty"`
+		Calls         []SimulateCallResult `json:"calls"`
+	}
+	var dec SimulateBlockResult
+	if err := json.Unmarshal(input, &dec); err != nil {
+		return err
+	}
+	if dec.Number != nil {
+		s.Number = uint64(*dec.Number)
+	}
+	if dec.Hash != nil {
+		s.Hash = *dec.Hash
+	}
+	if dec.Timestamp != nil {
+		s.Timestamp = uint64(*dec.Timestamp)
+	}
+	if dec.GasLimit != nil {
+		s.GasLimit = uint64(*dec.GasLimit)
+	}
+	if dec.GasUsed != nil {
+		s.GasUsed = uint64(*dec.GasUsed)
+	}
+	if dec.FeeRecipient != nil {
+		s.FeeRecipient = *dec.FeeRecipient
+	}
+	if dec.BaseFeePerGas != nil {
+		s.BaseFeePerGas = (*big.Int)(dec.BaseFeePerGas)
+	}
+	if dec.Calls != nil {
+		s.Calls = dec.Calls
+	}
+	return nil
+}
diff --git a/ethclient/gen_simulate_call_result.go b/ethclient/gen_simulate_call_result.go
new file mode 100644
index 0000000000..55e14cd697
--- /dev/null
+++ b/ethclient/gen_simulate_call_result.go
@@ -0,0 +1,61 @@
+// Code generated by github.com/fjl/gencodec. DO NOT EDIT.
+
+package ethclient
+
+import (
+	"encoding/json"
+
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/core/types"
+)
+
+var _ = (*simulateCallResultMarshaling)(nil)
+
+// MarshalJSON marshals as JSON.
+func (s SimulateCallResult) MarshalJSON() ([]byte, error) {
+	type SimulateCallResult struct {
+		ReturnValue hexutil.Bytes  `json:"returnData"`
+		Logs        []*types.Log   `json:"logs"`
+		GasUsed     hexutil.Uint64 `json:"gasUsed"`
+		Status      hexutil.Uint64 `json:"status"`
+		Error       *CallError     `json:"error,omitempty"`
+	}
+	var enc SimulateCallResult
+	enc.ReturnValue = s.ReturnValue
+	enc.Logs = s.Logs
+	enc.GasUsed = hexutil.Uint64(s.GasUsed)
+	enc.Status = hexutil.Uint64(s.Status)
+	enc.Error = s.Error
+	return json.Marshal(&enc)
+}
+
+// UnmarshalJSON unmarshals from JSON.
+func (s *SimulateCallResult) UnmarshalJSON(input []byte) error {
+	type SimulateCallResult struct {
+		ReturnValue *hexutil.Bytes  `json:"returnData"`
+		Logs        []*types.Log    `json:"logs"`
+		GasUsed     *hexutil.Uint64 `json:"gasUsed"`
+		Status      *hexutil.Uint64 `json:"status"`
+		Error       *CallError      `json:"error,omitempty"`
+	}
+	var dec SimulateCallResult
+	if err := json.Unmarshal(input, &dec); err != nil {
+		return err
+	}
+	if dec.ReturnValue != nil {
+		s.ReturnValue = *dec.ReturnValue
+	}
+	if dec.Logs != nil {
+		s.Logs = dec.Logs
+	}
+	if dec.GasUsed != nil {
+		s.GasUsed = uint64(*dec.GasUsed)
+	}
+	if dec.Status != nil {
+		s.Status = uint64(*dec.Status)
+	}
+	if dec.Error != nil {
+		s.Error = dec.Error
+	}
+	return nil
+}