diff --git a/cmd/evm/json_logger.go b/cmd/evm/json_logger.go
index 420b516763..a84d5daebd 100644
--- a/cmd/evm/json_logger.go
+++ b/cmd/evm/json_logger.go
@@ -26,23 +26,17 @@ import (
 	"github.com/ethereum/go-ethereum/core/vm"
 )
 
-// JSONLogger merely contains a writer, and immediately outputs to that channel,
-// instead of collecting logs
 type JSONLogger struct {
 	encoder *json.Encoder
 }
 
-// NewJSONLogger returns a new JSON logger
 func NewJSONLogger(writer io.Writer) *JSONLogger {
-	logger := &JSONLogger{
-		encoder: json.NewEncoder(writer),
-	}
-	return logger
+	return &JSONLogger{json.NewEncoder(writer)}
 }
 
-// CaptureState outputs state information on the logger
+// CaptureState outputs state information on the logger.
 func (l *JSONLogger) CaptureState(env *vm.EVM, pc uint64, op vm.OpCode, gas, cost uint64, memory *vm.Memory, stack *vm.Stack, contract *vm.Contract, depth int, err error) error {
-	log := vm.StructLog{
+	return l.encoder.Encode(vm.StructLog{
 		Pc:      pc,
 		Op:      op,
 		Gas:     gas + cost,
@@ -51,19 +45,16 @@ func (l *JSONLogger) CaptureState(env *vm.EVM, pc uint64, op vm.OpCode, gas, cos
 		Stack:   stack.Data(),
 		Storage: nil,
 		Depth:   depth,
-		Err:     err}
-	return l.encoder.Encode(log)
+		Err:     err,
+	})
 }
 
-// CaptureEnd is triggered at end of execution
+// CaptureEnd is triggered at end of execution.
 func (l *JSONLogger) CaptureEnd(output []byte, gasUsed uint64, t time.Duration) error {
 	type endLog struct {
 		Output  string              `json:"output"`
 		GasUsed math.HexOrDecimal64 `json:"gasUsed"`
 		Time    time.Duration       `json:"time"`
 	}
-
-	log := endLog{common.Bytes2Hex(output), math.HexOrDecimal64(gasUsed), t}
-	return l.encoder.Encode(log)
-
+	return l.encoder.Encode(endLog{common.Bytes2Hex(output), math.HexOrDecimal64(gasUsed), t})
 }
diff --git a/core/vm/gen_structlog.go b/core/vm/gen_structlog.go
index fec0e36196..1c86b2256f 100644
--- a/core/vm/gen_structlog.go
+++ b/core/vm/gen_structlog.go
@@ -7,6 +7,7 @@ import (
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/common/math"
 )
 
@@ -16,13 +17,13 @@ func (s StructLog) MarshalJSON() ([]byte, error) {
 		Op         OpCode                      `json:"op"`
 		Gas        math.HexOrDecimal64         `json:"gas"`
 		GasCost    math.HexOrDecimal64         `json:"gasCost"`
-		Memory     []byte                      `json:"memory"`
+		Memory     hexutil.Bytes               `json:"memory"`
 		Stack      []*math.HexOrDecimal256     `json:"stack"`
-		Storage    map[common.Hash]common.Hash `json:-`
+		Storage    map[common.Hash]common.Hash `json:"-"`
 		Depth      int                         `json:"depth"`
 		Err        error                       `json:"error"`
 		OpName     string                      `json:"opName"`
-		MemorySize string                      `json:"memSize"`
+		MemorySize int                         `json:"memSize"`
 	}
 	var enc StructLog
 	enc.Pc = s.Pc
@@ -50,9 +51,9 @@ func (s *StructLog) UnmarshalJSON(input []byte) error {
 		Op      *OpCode                     `json:"op"`
 		Gas     *math.HexOrDecimal64        `json:"gas"`
 		GasCost *math.HexOrDecimal64        `json:"gasCost"`
-		Memory  []byte                      `json:"memory"`
+		Memory  hexutil.Bytes               `json:"memory"`
 		Stack   []*math.HexOrDecimal256     `json:"stack"`
-		Storage map[common.Hash]common.Hash `json:-`
+		Storage map[common.Hash]common.Hash `json:"-"`
 		Depth   *int                        `json:"depth"`
 		Err     *error                      `json:"error"`
 	}
diff --git a/core/vm/logger.go b/core/vm/logger.go
index df9e3a514e..d95f462bc2 100644
--- a/core/vm/logger.go
+++ b/core/vm/logger.go
@@ -24,6 +24,7 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/common/math"
 	"github.com/ethereum/go-ethereum/core/types"
 )
@@ -58,7 +59,7 @@ type StructLog struct {
 	GasCost uint64                      `json:"gasCost"`
 	Memory  []byte                      `json:"memory"`
 	Stack   []*big.Int                  `json:"stack"`
-	Storage map[common.Hash]common.Hash `json:-`
+	Storage map[common.Hash]common.Hash `json:"-"`
 	Depth   int                         `json:"depth"`
 	Err     error                       `json:"error"`
 }
@@ -67,16 +68,17 @@ func (s *StructLog) OpName() string {
 	return s.Op.String()
 }
 
-func (s *StructLog) MemorySize() string {
-	return fmt.Sprintf("%v", len(s.Memory))
+func (s *StructLog) MemorySize() int {
+	return len(s.Memory)
 }
 
 type structLogMarshaling struct {
 	Stack      []*math.HexOrDecimal256
 	Gas        math.HexOrDecimal64
 	GasCost    math.HexOrDecimal64
+	Memory     hexutil.Bytes
 	OpName     string `json:"opName"`
-	MemorySize string `json:"memSize"`
+	MemorySize int    `json:"memSize"`
 }
 
 // Tracer is used to collect execution traces from an EVM transaction