diff --git a/vfs/dir_test.go b/vfs/dir_test.go
index 788471eb7..c04144e86 100644
--- a/vfs/dir_test.go
+++ b/vfs/dir_test.go
@@ -7,6 +7,7 @@ import (
 	"sort"
 	"testing"
 	"time"
+	"unsafe"
 
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fs/operations"
@@ -577,3 +578,7 @@ func TestDirRename(t *testing.T) {
 	err = dir.Rename("potato", "tuba", dir)
 	assert.Equal(t, EROFS, err)
 }
+
+func TestDirStructSize(t *testing.T) {
+	t.Logf("Dir struct has size %d bytes", unsafe.Sizeof(Dir{}))
+}
diff --git a/vfs/file_test.go b/vfs/file_test.go
index c54be40d1..728d8c699 100644
--- a/vfs/file_test.go
+++ b/vfs/file_test.go
@@ -6,6 +6,7 @@ import (
 	"io"
 	"os"
 	"testing"
+	"unsafe"
 
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fs/operations"
@@ -411,3 +412,7 @@ func TestFileRename(t *testing.T) {
 		})
 	}
 }
+
+func TestFileStructSize(t *testing.T) {
+	t.Logf("File struct has size %d bytes", unsafe.Sizeof(File{}))
+}