diff --git a/samples/flushfs/flush_fs_test.go b/samples/flushfs/flush_fs_test.go
index 646ebcb..cb62422 100644
--- a/samples/flushfs/flush_fs_test.go
+++ b/samples/flushfs/flush_fs_test.go
@@ -1027,5 +1027,6 @@ func (t *ReadOnlyTest) Chtimes() {
 }
 
 func (t *ReadOnlyTest) Chmod() {
-	AssertTrue(false, "TODO")
+	err := os.Chmod(path.Join(t.Dir, "foo"), 0700)
+	ExpectThat(err, Error(HasSubstr("read-only")))
 }