diff --git a/src/plugins/quota-clone/quota-clone-plugin.c b/src/plugins/quota-clone/quota-clone-plugin.c
index d99ed90a1d..8cddd05575 100644
--- a/src/plugins/quota-clone/quota-clone-plugin.c
+++ b/src/plugins/quota-clone/quota-clone-plugin.c
@@ -31,20 +31,15 @@ static MODULE_CONTEXT_DEFINE_INIT(quota_clone_storage_module,
 struct quota_clone_user {
 	union mail_user_module_context module_ctx;
 	struct dict *dict;
-	bool quota_flushing;
-};
-
-struct quota_clone_mailbox {
-	union mailbox_module_context module_ctx;
 	struct timeout *to_quota_flush;
 	bool quota_changed;
+	bool quota_flushing;
 };
 
-static void quota_clone_flush_real(struct mailbox *box)
+static void quota_clone_flush_real(struct mail_user *user)
 {
-	struct quota_clone_mailbox *qbox = QUOTA_CLONE_CONTEXT(box);
 	struct quota_clone_user *quser =
-		QUOTA_CLONE_USER_CONTEXT_REQUIRE(box->storage->user);
+		QUOTA_CLONE_USER_CONTEXT_REQUIRE(user);
 	struct dict_transaction_context *trans;
 	struct quota_root_iter *iter;
 	struct quota_root *root;
@@ -53,12 +48,12 @@ static void quota_clone_flush_real(struct mailbox *box)
 	enum quota_get_result bytes_res, count_res;
 
 	/* we'll clone the first quota root */
-	iter = quota_root_iter_init(box);
+	iter = quota_root_iter_init_user(user);
 	root = quota_root_iter_next(iter);
 	quota_root_iter_deinit(&iter);
 	if (root == NULL) {
-		/* no quota roots defined for this mailbox - ignore */
-		qbox->quota_changed = FALSE;
+		/* no quota roots defined - ignore */
+		quser->quota_changed = FALSE;
 		return;
 	}
 
@@ -109,103 +104,121 @@ static void quota_clone_flush_real(struct mailbox *box)
 	if (dict_transaction_commit(&trans, &error) < 0)
 		i_error("quota_clone_plugin: Failed to commit dict update: %s", error);
 	else
-		qbox->quota_changed = FALSE;
+		quser->quota_changed = FALSE;
 }
 
-static void quota_clone_flush(struct mailbox *box)
+static void quota_clone_flush(struct mail_user *user)
 {
-	struct quota_clone_mailbox *qbox = QUOTA_CLONE_CONTEXT(box);
 	struct quota_clone_user *quser =
-		QUOTA_CLONE_USER_CONTEXT_REQUIRE(box->storage->user);
+		QUOTA_CLONE_USER_CONTEXT_REQUIRE(user);
 
-	timeout_remove(&qbox->to_quota_flush);
+	timeout_remove(&quser->to_quota_flush);
 
 	if (quser->quota_flushing) {
 		/* recursing back from quota recalculation */
-	} else if (qbox->quota_changed) {
+	} else if (quser->quota_changed) {
 		quser->quota_flushing = TRUE;
-		quota_clone_flush_real(box);
+		quota_clone_flush_real(user);
 		quser->quota_flushing = FALSE;
 	}
 }
 
+static struct mail_user *quota_mailbox_get_user(struct mailbox *box)
+{
+	struct mail_namespace *ns = mailbox_list_get_namespace(box->list);
+	return ns->owner != NULL ? ns->owner : ns->user;
+}
+
 static void quota_clone_changed(struct mailbox *box)
 {
-	struct quota_clone_mailbox *qbox = QUOTA_CLONE_CONTEXT(box);
+	struct mail_user *user = quota_mailbox_get_user(box);
+	struct quota_clone_user *quser =
+		QUOTA_CLONE_USER_CONTEXT_REQUIRE(user);
 
-	qbox->quota_changed = TRUE;
-	if (qbox->to_quota_flush == NULL) {
-		qbox->to_quota_flush = timeout_add(QUOTA_CLONE_FLUSH_DELAY_MSECS,
-						   quota_clone_flush, box);
+	quser->quota_changed = TRUE;
+	if (quser->to_quota_flush == NULL) {
+		quser->to_quota_flush = timeout_add(QUOTA_CLONE_FLUSH_DELAY_MSECS,
+						    quota_clone_flush, user);
 	}
 }
 
 static int quota_clone_save_finish(struct mail_save_context *ctx)
 {
-	struct quota_clone_mailbox *qbox =
+	union mailbox_module_context *qbox =
 		QUOTA_CLONE_CONTEXT(ctx->transaction->box);
 
 	quota_clone_changed(ctx->transaction->box);
-	return qbox->module_ctx.super.save_finish(ctx);
+	return qbox->super.save_finish(ctx);
 }
 
 static int
 quota_clone_copy(struct mail_save_context *ctx, struct mail *mail)
 {
-	struct quota_clone_mailbox *qbox =
+	union mailbox_module_context *qbox =
 		QUOTA_CLONE_CONTEXT(ctx->transaction->box);
 
 	quota_clone_changed(ctx->transaction->box);
-	return qbox->module_ctx.super.copy(ctx, mail);
+	return qbox->super.copy(ctx, mail);
 }
 
 static void
 quota_clone_mailbox_sync_notify(struct mailbox *box, uint32_t uid,
 				enum mailbox_sync_type sync_type)
 {
-	struct quota_clone_mailbox *qbox = QUOTA_CLONE_CONTEXT(box);
+	union mailbox_module_context *qbox = QUOTA_CLONE_CONTEXT(box);
 
-	if (qbox->module_ctx.super.sync_notify != NULL)
-		qbox->module_ctx.super.sync_notify(box, uid, sync_type);
+	if (qbox->super.sync_notify != NULL)
+		qbox->super.sync_notify(box, uid, sync_type);
 
 	if (sync_type == MAILBOX_SYNC_TYPE_EXPUNGE)
 		quota_clone_changed(box);
 }
 
-static void quota_clone_mailbox_close(struct mailbox *box)
-{
-	struct quota_clone_mailbox *qbox = QUOTA_CLONE_CONTEXT(box);
-
-	qbox->module_ctx.super.close(box);
-
-	quota_clone_flush(box);
-}
-
 static void quota_clone_mailbox_allocated(struct mailbox *box)
 {
 	struct quota_clone_user *quser =
 		QUOTA_CLONE_USER_CONTEXT(box->storage->user);
 	struct mailbox_vfuncs *v = box->vlast;
-	struct quota_clone_mailbox *qbox;
+	union mailbox_module_context *qbox;
 
 	if (quser == NULL)
 		return;
 
-	qbox = p_new(box->pool, struct quota_clone_mailbox, 1);
-	qbox->module_ctx.super = *v;
-	box->vlast = &qbox->module_ctx.super;
+	qbox = p_new(box->pool, union mailbox_module_context, 1);
+	qbox->super = *v;
+	box->vlast = &qbox->super;
 
 	v->save_finish = quota_clone_save_finish;
 	v->copy = quota_clone_copy;
 	v->sync_notify = quota_clone_mailbox_sync_notify;
-	v->close = quota_clone_mailbox_close;
-	MODULE_CONTEXT_SET(box, quota_clone_storage_module, qbox);
+	MODULE_CONTEXT_SET_SELF(box, quota_clone_storage_module, qbox);
+}
+
+static void quota_clone_mail_user_deinit_pre(struct mail_user *user)
+{
+	struct quota_clone_user *quser = QUOTA_CLONE_USER_CONTEXT_REQUIRE(user);
+
+	dict_wait(quser->dict);
+	/* Check once more if quota needs to be updated. This needs to be done
+	   in deinit_pre(), because at deinit() the quota is already
+	   deinitialized. */
+	if (quser->to_quota_flush != NULL) {
+		i_assert(!quser->quota_flushing);
+		quota_clone_flush(user);
+		dict_wait(quser->dict);
+		i_assert(quser->to_quota_flush == NULL);
+	}
+	quser->module_ctx.super.deinit_pre(user);
 }
 
 static void quota_clone_mail_user_deinit(struct mail_user *user)
 {
 	struct quota_clone_user *quser = QUOTA_CLONE_USER_CONTEXT_REQUIRE(user);
 
+	/* wait once more, just in case something changed quota during
+	   deinit_pre() */
+	dict_wait(quser->dict);
+	i_assert(quser->to_quota_flush == NULL);
 	dict_deinit(&quser->dict);
 	quser->module_ctx.super.deinit(user);
 }
@@ -239,6 +252,7 @@ static void quota_clone_mail_user_created(struct mail_user *user)
 	quser = p_new(user->pool, struct quota_clone_user, 1);
 	quser->module_ctx.super = *v;
 	user->vlast = &quser->module_ctx.super;
+	v->deinit_pre = quota_clone_mail_user_deinit_pre;
 	v->deinit = quota_clone_mail_user_deinit;
 	quser->dict = dict;
 	MODULE_CONTEXT_SET(user, quota_clone_user_module, quser);