diff --git a/packages/common/infra/src/modules/workspace/impls/storage.ts b/packages/common/infra/src/modules/workspace/impls/storage.ts
index 24223987dc..fd85f0ff4c 100644
--- a/packages/common/infra/src/modules/workspace/impls/storage.ts
+++ b/packages/common/infra/src/modules/workspace/impls/storage.ts
@@ -19,7 +19,7 @@ export class WorkspaceLocalStateImpl implements WorkspaceLocalState {
     return this.wrapped.keys();
   }
 
-  get<T>(key: string): T | null {
+  get<T>(key: string): T | undefined {
     return this.wrapped.get<T>(key);
   }
 
@@ -27,7 +27,7 @@ export class WorkspaceLocalStateImpl implements WorkspaceLocalState {
     return this.wrapped.watch<T>(key);
   }
 
-  set<T>(key: string, value: T | null): void {
+  set<T>(key: string, value: T): void {
     return this.wrapped.set<T>(key, value);
   }
 
@@ -53,7 +53,7 @@ export class WorkspaceLocalCacheImpl implements WorkspaceLocalCache {
     return this.wrapped.keys();
   }
 
-  get<T>(key: string): T | null {
+  get<T>(key: string): T | undefined {
     return this.wrapped.get<T>(key);
   }
 
@@ -61,7 +61,7 @@ export class WorkspaceLocalCacheImpl implements WorkspaceLocalCache {
     return this.wrapped.watch<T>(key);
   }
 
-  set<T>(key: string, value: T | null): void {
+  set<T>(key: string, value: T): void {
     return this.wrapped.set<T>(key, value);
   }
 
diff --git a/packages/common/infra/src/storage/__tests__/memento.spec.ts b/packages/common/infra/src/storage/__tests__/memento.spec.ts
index e037ab98f4..1416dc5e9e 100644
--- a/packages/common/infra/src/storage/__tests__/memento.spec.ts
+++ b/packages/common/infra/src/storage/__tests__/memento.spec.ts
@@ -6,7 +6,7 @@ describe('memento', () => {
   test('memory', () => {
     const memento = new MemoryMemento();
 
-    expect(memento.get('foo')).toBeNull();
+    expect(memento.get('foo')).toBeUndefined();
     memento.set('foo', 'bar');
     expect(memento.get('foo')).toEqual('bar');
 
diff --git a/packages/common/infra/src/storage/memento.ts b/packages/common/infra/src/storage/memento.ts
index aec1d4d193..0a2fe069e0 100644
--- a/packages/common/infra/src/storage/memento.ts
+++ b/packages/common/infra/src/storage/memento.ts
@@ -6,9 +6,9 @@ import { LiveData } from '../livedata';
  * A memento represents a storage utility. It can store and retrieve values, and observe changes.
  */
 export interface Memento {
-  get<T>(key: string): T | null;
-  watch<T>(key: string): Observable<T | null>;
-  set<T>(key: string, value: T | null): void;
+  get<T>(key: string): T | undefined;
+  watch<T>(key: string): Observable<T | undefined>;
+  set<T>(key: string, value: T | undefined): void;
   del(key: string): void;
   clear(): void;
   keys(): string[];
@@ -23,19 +23,19 @@ export class MemoryMemento implements Memento {
   private getLiveData(key: string): LiveData<any> {
     let data$ = this.data.get(key);
     if (!data$) {
-      data$ = new LiveData<any>(null);
+      data$ = new LiveData<any>(undefined);
       this.data.set(key, data$);
     }
     return data$;
   }
 
-  get<T>(key: string): T | null {
+  get<T>(key: string): T | undefined {
     return this.getLiveData(key).value;
   }
-  watch<T>(key: string): Observable<T | null> {
+  watch<T>(key: string): Observable<T | undefined> {
     return this.getLiveData(key).asObservable();
   }
-  set<T>(key: string, value: T | null): void {
+  set<T>(key: string, value: T): void {
     this.getLiveData(key).next(value);
   }
   keys(): string[] {
@@ -51,13 +51,13 @@ export class MemoryMemento implements Memento {
 
 export function wrapMemento(memento: Memento, prefix: string): Memento {
   return {
-    get<T>(key: string): T | null {
+    get<T>(key: string): T | undefined {
       return memento.get(prefix + key);
     },
     watch(key: string) {
       return memento.watch(prefix + key);
     },
-    set<T>(key: string, value: T | null): void {
+    set<T>(key: string, value: T): void {
       memento.set(prefix + key, value);
     },
     keys(): string[] {
diff --git a/packages/frontend/core/src/components/affine/reference-link/index.tsx b/packages/frontend/core/src/components/affine/reference-link/index.tsx
index 469cee0f27..2ba74605e4 100644
--- a/packages/frontend/core/src/components/affine/reference-link/index.tsx
+++ b/packages/frontend/core/src/components/affine/reference-link/index.tsx
@@ -84,8 +84,8 @@ export function AffinePageReference({
   const t = useI18n();
 
   const docsService = useService(DocsService);
-  const mode$ = LiveData.from(docsService.list.observeMode(pageId), null);
-  const docMode = useLiveData(mode$);
+  const mode$ = LiveData.from(docsService.list.observeMode(pageId), undefined);
+  const docMode = useLiveData(mode$) ?? null;
   const el = pageReferenceRenderer({
     docMode,
     pageId,
diff --git a/packages/frontend/core/src/modules/storage/impls/storage.ts b/packages/frontend/core/src/modules/storage/impls/storage.ts
index 375157285b..141f6a0b5b 100644
--- a/packages/frontend/core/src/modules/storage/impls/storage.ts
+++ b/packages/frontend/core/src/modules/storage/impls/storage.ts
@@ -15,14 +15,14 @@ export class LocalStorageMemento implements Memento {
     return keys;
   }
 
-  get<T>(key: string): T | null {
+  get<T>(key: string): T | undefined {
     const json = localStorage.getItem(this.prefix + key);
-    return json ? JSON.parse(json) : null;
+    return json ? JSON.parse(json) : undefined;
   }
-  watch<T>(key: string): Observable<T | null> {
-    return new Observable<T | null>(subscriber => {
+  watch<T>(key: string): Observable<T | undefined> {
+    return new Observable<T | undefined>(subscriber => {
       const json = localStorage.getItem(this.prefix + key);
-      const first = json ? JSON.parse(json) : null;
+      const first = json ? JSON.parse(json) : undefined;
       subscriber.next(first);
 
       const channel = new BroadcastChannel(this.prefix + key);
@@ -34,7 +34,7 @@ export class LocalStorageMemento implements Memento {
       };
     });
   }
-  set<T>(key: string, value: T | null): void {
+  set<T>(key: string, value: T): void {
     localStorage.setItem(this.prefix + key, JSON.stringify(value));
     const channel = new BroadcastChannel(this.prefix + key);
     channel.postMessage(value);