diff --git a/packages/frontend/src/lib/pizzax.ts b/packages/frontend/src/lib/pizzax.ts
index 0dd8a82957..51e3daae9f 100644
--- a/packages/frontend/src/lib/pizzax.ts
+++ b/packages/frontend/src/lib/pizzax.ts
@@ -82,8 +82,10 @@ export class Pizzax<T extends StateDef> {
 		this.r = {} as ReactiveState<T>;
 
 		for (const [k, v] of Object.entries(def) as [keyof T, T[keyof T]['default']][]) {
-			this.s[k] = v.default;
-			this.r[k] = ref(v.default);
+			// 参照渡しになるのを防ぐためclone
+			const defaultValue = deepClone(v.default);
+			this.s[k] = defaultValue;
+			this.r[k] = ref(defaultValue);
 		}
 
 		this.ready = this.init();
@@ -120,7 +122,8 @@ export class Pizzax<T extends StateDef> {
 			} else if (v.where === 'deviceAccount' && Object.prototype.hasOwnProperty.call(deviceAccountState, k)) {
 				this.r[k].value = this.s[k] = this.mergeState<T[keyof T]['default']>(deviceAccountState[k], v.default);
 			} else {
-				this.r[k].value = this.s[k] = v.default;
+				// 参照渡しになるのを防ぐためclone
+				this.r[k].value = this.s[k] = deepClone(v.default);
 			}
 		}
 
@@ -148,7 +151,8 @@ export class Pizzax<T extends StateDef> {
 										this.r[k].value = this.s[k] = (kvs as Partial<T>)[k];
 										cache[k] = (kvs as Partial<T>)[k];
 									} else {
-										this.r[k].value = this.s[k] = v.default;
+										// 参照渡しになるのを防ぐためclone
+										this.r[k].value = this.s[k] = deepClone(v.default);
 									}
 								}
 							}
@@ -218,8 +222,10 @@ export class Pizzax<T extends StateDef> {
 	}
 
 	public reset(key: keyof T) {
-		this.set(key, this.def[key].default);
-		return this.def[key].default;
+		// 参照渡しになるのを防ぐためclone
+		const defaultValue = deepClone(this.def[key].default);
+		this.set(key, defaultValue);
+		return defaultValue;
 	}
 
 	/**
diff --git a/packages/frontend/src/preferences/manager.ts b/packages/frontend/src/preferences/manager.ts
index 7f3949f81b..9a2056271f 100644
--- a/packages/frontend/src/preferences/manager.ts
+++ b/packages/frontend/src/preferences/manager.ts
@@ -14,6 +14,7 @@ import { copyToClipboard } from '@/utility/copy-to-clipboard.js';
 import { i18n } from '@/i18n.js';
 import * as os from '@/os.js';
 import { deepEqual } from '@/utility/deep-equal.js';
+import { deepClone } from '@/utility/clone.js';
 
 // NOTE: 明示的な設定値のひとつとして null もあり得るため、設定が存在しないかどうかを判定する目的で null で比較したり ?? を使ってはいけない
 
@@ -122,7 +123,8 @@ export function getInitialPrefValue<K extends keyof PREF>(k: K): ValueOf<K> {
 	if (typeof _default === 'function') { // factory
 		return _default() as ValueOf<K>;
 	} else {
-		return _default as unknown as ValueOf<K>;
+		// 参照渡しになるのを防ぐためclone
+		return deepClone(_default as unknown as ValueOf<K>);
 	}
 }