diff --git a/cephfs/file_test.go b/cephfs/file_test.go
index cd10262..ae00f4f 100644
--- a/cephfs/file_test.go
+++ b/cephfs/file_test.go
@@ -409,4 +409,9 @@ func TestFchown(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, uint32(stats.Sys().(*syscall.Stat_t).Uid), bob)
 	assert.Equal(t, uint32(stats.Sys().(*syscall.Stat_t).Gid), bob)
+
+	// TODO use t.Run sub-tests where appropriate
+	f2 := &File{}
+	err = f2.Fchown(bob, bob)
+	assert.Error(t, err)
 }