diff --git a/src/client/account.ts b/src/client/account.ts
index 1ba7a28908..5519fd028c 100644
--- a/src/client/account.ts
+++ b/src/client/account.ts
@@ -1,4 +1,4 @@
-import { get, set } from 'idb-keyval';
+import { get, set } from '@/scripts/idb-proxy';
 import { reactive } from 'vue';
 import { apiUrl } from '@/config';
 import { waiting } from '@/os';
diff --git a/src/client/init.ts b/src/client/init.ts
index 264ecaf8d1..28d919e8b9 100644
--- a/src/client/init.ts
+++ b/src/client/init.ts
@@ -4,7 +4,7 @@
 
 import '@/style.scss';
 
-import { set } from 'idb-keyval';
+import { set } from '@/scripts/idb-proxy';
 
 // TODO: そのうち消す
 if (localStorage.getItem('vuex') != null) {
diff --git a/src/client/scripts/get-account-from-id.ts b/src/client/scripts/get-account-from-id.ts
index be4cfaeba4..ba3adceecc 100644
--- a/src/client/scripts/get-account-from-id.ts
+++ b/src/client/scripts/get-account-from-id.ts
@@ -1,4 +1,4 @@
-import { get } from 'idb-keyval';
+import { get } from '@/scripts/idb-proxy';
 
 export async function getAccountFromId(id: string) {
 	const accounts = await get('accounts') as { token: string; id: string; }[];
diff --git a/src/client/scripts/idb-proxy.ts b/src/client/scripts/idb-proxy.ts
new file mode 100644
index 0000000000..986e8ee8dc
--- /dev/null
+++ b/src/client/scripts/idb-proxy.ts
@@ -0,0 +1,23 @@
+// FirefoxのプライベートモードなどではindexedDBが使用不可能なので、使う
+import {
+    get as iget,
+    set as iset,
+    del as idel
+} from 'idb-keyval';
+
+const fallbackName = (key: string) => `idbfallback::${key}`; 
+
+export async function get(key: string) {
+    if (window.indexedDB) return iget(key);
+    return JSON.parse(localStorage.getItem(fallbackName(key)) || 'null');
+}
+
+export async function set(key: string, val: any) {
+    if (window.indexedDB) return iset(key, val);
+    return localStorage.setItem(fallbackName(key), JSON.stringify(val));
+}
+
+export async function del(key: string) {
+    if (window.indexedDB) return idel(key);
+    return localStorage.removeItem(fallbackName(key));
+}
diff --git a/src/client/sw/lang.ts b/src/client/sw/lang.ts
index 1b3f1ad620..99f0e518c3 100644
--- a/src/client/sw/lang.ts
+++ b/src/client/sw/lang.ts
@@ -3,7 +3,7 @@
  */
 declare var self: ServiceWorkerGlobalScope;
 
-import { get, set } from 'idb-keyval';
+import { get, set } from '@/scripts/idb-proxy';
 import { I18n } from '../../misc/i18n';
 
 class SwLang {
diff --git a/src/client/sw/notification-read.ts b/src/client/sw/notification-read.ts
index 093322a8b7..03cb0611ca 100644
--- a/src/client/sw/notification-read.ts
+++ b/src/client/sw/notification-read.ts
@@ -1,6 +1,6 @@
 declare var self: ServiceWorkerGlobalScope;
 
-import { get } from 'idb-keyval';
+import { get } from '@/scripts/idb-proxy';
 import { pushNotificationData } from '../../types';
 import { api } from './operations';