diff --git a/blocksuite/framework/store/src/__tests__/block.unit.spec.ts b/blocksuite/framework/store/src/__tests__/block.unit.spec.ts
index 6806714c9..f6175f668 100644
--- a/blocksuite/framework/store/src/__tests__/block.unit.spec.ts
+++ b/blocksuite/framework/store/src/__tests__/block.unit.spec.ts
@@ -51,6 +51,7 @@ const flatTableSchema = defineBlockSchema({
     textCols: {} as Record<string, Text>,
     rows: {} as Record<string, { color: string }>,
     labels: [] as Array<string>,
+    optional: undefined as string | undefined,
   }),
   metadata: {
     role: 'content',
@@ -494,6 +495,16 @@ describe('flat', () => {
     expect(model.props.textCols$.value.a.toDelta()).toEqual([
       { insert: 'test' },
     ]);
+
+    onChange.mockClear();
+    expect(model.props).not.toHaveProperty('optional');
+    expect(model.props).toHaveProperty('optional$');
+    model.props.optional$.value = 'test';
+    expect(model.props.optional).toBe('test');
+    expect(model.props.optional$.value).toBe('test');
+    expect(onChange).toHaveBeenCalledTimes(1);
+    expect(onChange).toHaveBeenCalledWith(expect.anything(), 'optional', true);
+    expect(yBlock.get('prop:optional')).toBe('test');
   });
 
   test('stash and pop', () => {
diff --git a/blocksuite/framework/store/src/model/block/flat-sync-controller.ts b/blocksuite/framework/store/src/model/block/flat-sync-controller.ts
index 293410b05..a8231c4a3 100644
--- a/blocksuite/framework/store/src/model/block/flat-sync-controller.ts
+++ b/blocksuite/framework/store/src/model/block/flat-sync-controller.ts
@@ -47,6 +47,7 @@ export class FlatSyncController {
     }
 
     const model = schema.model.toModel?.() ?? new BlockModel<object>();
+    const defaultProps = schema.model.props?.(internalPrimitives);
     model.schema = schema;
 
     model.id = this.id;
@@ -55,7 +56,8 @@ export class FlatSyncController {
     const reactive = new ReactiveFlatYMap(
       this.yBlock,
       model.deleted,
-      this.onChange
+      this.onChange,
+      defaultProps
     );
     this._reactive = reactive;
     const proxy = reactive.proxy;
@@ -66,17 +68,6 @@ export class FlatSyncController {
       model.store = this.doc;
     }
 
-    const defaultProps = schema.model.props?.(internalPrimitives);
-    if (defaultProps) {
-      Object.entries(defaultProps).forEach(([key, value]) => {
-        if (key in proxy) {
-          return;
-        }
-        if (value === undefined) return;
-        proxy[key] = value;
-      });
-    }
-
     return model;
   }
 
diff --git a/blocksuite/framework/store/src/reactive/flat-native-y/index.ts b/blocksuite/framework/store/src/reactive/flat-native-y/index.ts
index 7bee39560..6fb9b707b 100644
--- a/blocksuite/framework/store/src/reactive/flat-native-y/index.ts
+++ b/blocksuite/framework/store/src/reactive/flat-native-y/index.ts
@@ -99,7 +99,8 @@ export class ReactiveFlatYMap extends BaseReactiveYData<
   constructor(
     protected readonly _ySource: YMap<unknown>,
     private readonly _onDispose: Subject<void>,
-    private readonly _onChange?: OnChange
+    private readonly _onChange?: OnChange,
+    defaultProps?: Record<string, unknown>
   ) {
     super();
     this._initialized = false;
@@ -112,7 +113,7 @@ export class ReactiveFlatYMap extends BaseReactiveYData<
 
     const proxy = this._getProxy(source, source);
 
-    Object.entries(source).forEach(([key, value]) => {
+    const initSignals = (key: string, value: unknown) => {
       const signalData = signal(value);
       source[`${key}$`] = signalData;
       const unsubscribe = signalData.subscribe(next => {
@@ -128,11 +129,30 @@ export class ReactiveFlatYMap extends BaseReactiveYData<
         subscription.unsubscribe();
         unsubscribe();
       });
+    };
+
+    Object.entries(source).forEach(([key, value]) => {
+      initSignals(key, value);
     });
 
+    if (defaultProps) {
+      Object.entries(defaultProps).forEach(([key, value]) => {
+        if (!(key in proxy) && value === undefined) {
+          initSignals(key, value);
+        }
+      });
+    }
+
     this._proxy = proxy;
     this._ySource.observe(this._observer);
     this._initialized = true;
+
+    if (defaultProps) {
+      Object.entries(defaultProps).forEach(([key, value]) => {
+        if (key in proxy || value === undefined) return;
+        proxy[key] = value;
+      });
+    }
   }
 
   pop = (prop: string): void => {