diff --git a/src/vs/vscode.proposed.d.ts b/src/vs/vscode.proposed.d.ts
index 3941734f218..1b758f27f63 100644
--- a/src/vs/vscode.proposed.d.ts
+++ b/src/vs/vscode.proposed.d.ts
@@ -1373,7 +1373,7 @@ declare module 'vscode' {
 
 	export class NotebookData {
 		cells: NotebookCellData[];
-		metadata?: NotebookDocumentMetadata;
+		metadata: NotebookDocumentMetadata;
 		constructor(cells: NotebookCellData[], metadata?: NotebookDocumentMetadata);
 	}
 
diff --git a/src/vs/workbench/api/common/extHostNotebook.ts b/src/vs/workbench/api/common/extHostNotebook.ts
index bfc5a78f8aa..15dc624965a 100644
--- a/src/vs/workbench/api/common/extHostNotebook.ts
+++ b/src/vs/workbench/api/common/extHostNotebook.ts
@@ -17,7 +17,7 @@ import { IExtensionStoragePaths } from 'vs/workbench/api/common/extHostStoragePa
 import * as typeConverters from 'vs/workbench/api/common/extHostTypeConverters';
 import * as extHostTypes from 'vs/workbench/api/common/extHostTypes';
 import { asWebviewUri, WebviewInitData } from 'vs/workbench/api/common/shared/webview';
-import { CellStatusbarAlignment, CellUri, INotebookCellStatusBarEntry, INotebookExclusiveDocumentFilter, NotebookCellMetadata, NotebookCellsChangedEventDto, NotebookCellsChangeType, NotebookDataDto, notebookDocumentMetadataDefaults } from 'vs/workbench/contrib/notebook/common/notebookCommon';
+import { CellStatusbarAlignment, CellUri, INotebookCellStatusBarEntry, INotebookExclusiveDocumentFilter, NotebookCellMetadata, NotebookCellsChangedEventDto, NotebookCellsChangeType, NotebookDataDto } from 'vs/workbench/contrib/notebook/common/notebookCommon';
 import * as vscode from 'vscode';
 import { ResourceMap } from 'vs/base/common/map';
 import { ExtHostCell, ExtHostNotebookDocument } from './extHostNotebookDocument';
@@ -502,10 +502,7 @@ export class ExtHostNotebookController implements ExtHostNotebookShape {
 		const { provider } = this._getProviderData(viewType);
 		const data = await provider.openNotebook(URI.revive(uri), { backupId, untitledDocumentData: untitledDocumentData?.buffer }, token);
 		return {
-			metadata: {
-				...notebookDocumentMetadataDefaults,
-				...data.metadata
-			},
+			metadata: typeConverters.NotebookDocumentMetadata.from(data.metadata),
 			cells: data.cells.map(typeConverters.NotebookCellData.from),
 		};
 	}
diff --git a/src/vs/workbench/api/common/extHostNotebookEditor.ts b/src/vs/workbench/api/common/extHostNotebookEditor.ts
index 6051b41b728..6f8a7a5f8cd 100644
--- a/src/vs/workbench/api/common/extHostNotebookEditor.ts
+++ b/src/vs/workbench/api/common/extHostNotebookEditor.ts
@@ -7,7 +7,7 @@ import { Emitter, Event } from 'vs/base/common/event';
 import { MainThreadNotebookShape } from 'vs/workbench/api/common/extHost.protocol';
 import * as extHostTypes from 'vs/workbench/api/common/extHostTypes';
 import * as extHostConverter from 'vs/workbench/api/common/extHostTypeConverters';
-import { CellEditType, ICellEditOperation, ICellReplaceEdit, notebookDocumentMetadataDefaults } from 'vs/workbench/contrib/notebook/common/notebookCommon';
+import { CellEditType, ICellEditOperation, ICellReplaceEdit } from 'vs/workbench/contrib/notebook/common/notebookCommon';
 import * as vscode from 'vscode';
 import { ExtHostNotebookDocument } from './extHostNotebookDocument';
 
@@ -45,7 +45,7 @@ class NotebookEditorCellEditBuilder implements vscode.NotebookEditorEdit {
 		this._throwIfFinalized();
 		this._collectedEdits.push({
 			editType: CellEditType.DocumentMetadata,
-			metadata: { ...notebookDocumentMetadataDefaults, ...value }
+			metadata: value
 		});
 	}
 
diff --git a/src/vs/workbench/api/common/extHostTypes.ts b/src/vs/workbench/api/common/extHostTypes.ts
index 4103b64c025..88833b1730f 100644
--- a/src/vs/workbench/api/common/extHostTypes.ts
+++ b/src/vs/workbench/api/common/extHostTypes.ts
@@ -13,7 +13,7 @@ import { URI } from 'vs/base/common/uri';
 import { generateUuid } from 'vs/base/common/uuid';
 import { FileSystemProviderErrorCode, markAsFileSystemProviderError } from 'vs/platform/files/common/files';
 import { RemoteAuthorityResolverErrorCode } from 'vs/platform/remote/common/remoteAuthorityResolver';
-import { CellEditType, ICellEditOperation, notebookDocumentMetadataDefaults } from 'vs/workbench/contrib/notebook/common/notebookCommon';
+import { CellEditType, ICellEditOperation } from 'vs/workbench/contrib/notebook/common/notebookCommon';
 import type * as vscode from 'vscode';
 
 function es5ClassCompat(target: Function): any {
@@ -673,7 +673,7 @@ export class WorkspaceEdit implements vscode.WorkspaceEdit {
 	// --- notebook
 
 	replaceNotebookMetadata(uri: URI, value: vscode.NotebookDocumentMetadata, metadata?: vscode.WorkspaceEditEntryMetadata): void {
-		this._edits.push({ _type: FileEditType.Cell, metadata, uri, edit: { editType: CellEditType.DocumentMetadata, metadata: { ...notebookDocumentMetadataDefaults, ...value } }, notebookMetadata: value });
+		this._edits.push({ _type: FileEditType.Cell, metadata, uri, edit: { editType: CellEditType.DocumentMetadata, metadata: value }, notebookMetadata: value });
 	}
 
 	replaceNotebookCells(uri: URI, start: number, end: number, cells: vscode.NotebookCellData[], metadata?: vscode.WorkspaceEditEntryMetadata): void {
@@ -3138,11 +3138,11 @@ export class NotebookCellData {
 export class NotebookData {
 
 	cells: NotebookCellData[];
-	metadata?: NotebookDocumentMetadata;
+	metadata: NotebookDocumentMetadata;
 
 	constructor(cells: NotebookCellData[], metadata?: NotebookDocumentMetadata) {
 		this.cells = cells;
-		this.metadata = metadata;
+		this.metadata = metadata ?? new NotebookDocumentMetadata();
 	}
 }