diff --git a/feature_reflect_slice.go b/feature_reflect_slice.go
index 1a1a2ab..51a8dae 100644
--- a/feature_reflect_slice.go
+++ b/feature_reflect_slice.go
@@ -127,10 +127,10 @@ func growOne(slice *sliceHeader, sliceType reflect.Type, elementType reflect.Typ
 	newVal := reflect.MakeSlice(sliceType, newLen, newCap)
 	dst := unsafe.Pointer(newVal.Pointer())
 	// copy old array into new array
-	originalBytesCount := uintptr(slice.Len) * elementType.Size()
-	srcPtr := (*[1 << 49]byte)(slice.Data)
-	dstPtr := (*[1 << 49]byte)(dst)
-	copy(dstPtr[:originalBytesCount], srcPtr[:originalBytesCount])
+	originalBytesCount := slice.Len * int(elementType.Size())
+	srcSliceHeader := (unsafe.Pointer)(&sliceHeader{slice.Data, originalBytesCount, originalBytesCount})
+	dstSliceHeader := (unsafe.Pointer)(&sliceHeader{dst, originalBytesCount, originalBytesCount})
+	copy(*(*[]byte)(dstSliceHeader), *(*[]byte)(srcSliceHeader))
 	slice.Data = dst
 	slice.Len = newLen
 	slice.Cap = newCap
diff --git a/jsoniter_interface_test.go b/jsoniter_interface_test.go
index e5f3283..3245d68 100644
--- a/jsoniter_interface_test.go
+++ b/jsoniter_interface_test.go
@@ -11,6 +11,7 @@ import (
 )
 
 func Test_write_empty_interface_via_placeholder(t *testing.T) {
+	fmt.Println(^uint(0) >> 1)
 	should := require.New(t)
 	m := map[uint32]interface{}{1:"hello"}
 	inf := reflect.ValueOf(m).MapIndex(reflect.ValueOf(uint32(1))).Interface()