diff --git a/core/types/block.go b/core/types/block.go
index 8a21bba1e7..9ea3c9f128 100644
--- a/core/types/block.go
+++ b/core/types/block.go
@@ -24,7 +24,6 @@ import (
 	"sort"
 	"sync/atomic"
 	"time"
-	"unsafe"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
@@ -105,7 +104,8 @@ func (h *Header) Hash() common.Hash {
 // Size returns the approximate memory used by all internal contents. It is used
 // to approximate and limit the memory consumption of various caches.
 func (h *Header) Size() common.StorageSize {
-	return common.StorageSize(unsafe.Sizeof(*h)) + common.StorageSize(len(h.Extra)+(h.Difficulty.BitLen()+h.Number.BitLen()+h.Time.BitLen())/8)
+	size := binary.Size(h)
+	return common.StorageSize(size) + common.StorageSize(len(h.Extra)+(h.Difficulty.BitLen()+h.Number.BitLen()+h.Time.BitLen())/8)
 }
 
 func rlpHash(x interface{}) (h common.Hash) {