diff --git a/extensions/image-preview/src/preview.ts b/extensions/image-preview/src/preview.ts
index 90b5fbd4c9607f0892b48078723af4d6968fbc2b..815df001baaf0affd7e3df305be360693ffa347e 100644
--- a/extensions/image-preview/src/preview.ts
+++ b/extensions/image-preview/src/preview.ts
@@ -28,7 +28,7 @@ export class PreviewManager implements vscode.CustomEditorProvider {
 	) { }
 
 	public async openCustomDocument(uri: vscode.Uri) {
-		return new vscode.CustomDocument(PreviewManager.viewType, uri);
+		return new vscode.CustomDocument(uri);
 	}
 
 	public async resolveCustomEditor(
diff --git a/extensions/markdown-language-features/src/features/previewManager.ts b/extensions/markdown-language-features/src/features/previewManager.ts
index 78b2aa65107aaf1ab5d778fa6879234ece6d8fa2..98c3c9a776acdab8bae1d81594c6f7087b780845 100644
--- a/extensions/markdown-language-features/src/features/previewManager.ts
+++ b/extensions/markdown-language-features/src/features/previewManager.ts
@@ -151,7 +151,7 @@ export class MarkdownPreviewManager extends Disposable implements vscode.Webview
 	}
 
 	public async openCustomDocument(uri: vscode.Uri) {
-		return new vscode.CustomDocument(this.customEditorViewType, uri);
+		return new vscode.CustomDocument(uri);
 	}
 
 	public async resolveCustomTextEditor(
diff --git a/src/vs/vscode.d.ts b/src/vs/vscode.d.ts
index 307737aa174f2472bf2b0cc493f211751dc05acc..ae1d7cb310b0d30cc50d5163ef7816684277ddf6 100644
--- a/src/vs/vscode.d.ts
+++ b/src/vs/vscode.d.ts
@@ -7006,15 +7006,9 @@ declare module 'vscode' {
 	 */
 	class CustomDocument<EditType = unknown> {
 		/**
-		 * @param viewType The associated uri for this document.
 		 * @param uri The associated viewType for this document.
 		 */
-		constructor(viewType: string, uri: Uri);
-
-		/**
-		 * The associated viewType for this document.
-		 */
-		readonly viewType: string;
+		constructor(uri: Uri);
 
 		/**
 		 * The associated uri for this document.
diff --git a/src/vs/workbench/api/common/extHostTypes.ts b/src/vs/workbench/api/common/extHostTypes.ts
index fbd06153344f77cebee0f2e8ddd9184194606571..76f40cb3852a9801905d55c05cfc0e918c7772b3 100644
--- a/src/vs/workbench/api/common/extHostTypes.ts
+++ b/src/vs/workbench/api/common/extHostTypes.ts
@@ -2747,7 +2747,6 @@ export class CustomDocument<EditType = unknown> implements vscode.CustomDocument
 
 	readonly #edits = new Cache<EditType>('edits');
 
-	readonly #viewType: string;
 	readonly #uri: vscode.Uri;
 
 	#editState: EditState = {
@@ -2758,15 +2757,12 @@ export class CustomDocument<EditType = unknown> implements vscode.CustomDocument
 	#isDisposed = false;
 	#version = 1;
 
-	constructor(viewType: string, uri: vscode.Uri) {
-		this.#viewType = viewType;
+	constructor(uri: vscode.Uri) {
 		this.#uri = uri;
 	}
 
 	//#region Public API
 
-	public get viewType(): string { return this.#viewType; }
-
 	public get uri(): vscode.Uri { return this.#uri; }
 
 	public get fileName(): string { return this.uri.fsPath; }
diff --git a/src/vs/workbench/api/common/extHostWebview.ts b/src/vs/workbench/api/common/extHostWebview.ts
index d5b0d496c021ff25b21267626c56109a18633267..aced97ccc25ebbbaa3093cf6a06e7c35f58911c7 100644
--- a/src/vs/workbench/api/common/extHostWebview.ts
+++ b/src/vs/workbench/api/common/extHostWebview.ts
@@ -269,16 +269,16 @@ class WebviewDocumentStore {
 		return this._documents.get(this.key(viewType, resource));
 	}
 
-	public add(document: extHostTypes.CustomDocument) {
-		const key = this.key(document.viewType, document.uri);
+	public add(viewType: string, document: extHostTypes.CustomDocument) {
+		const key = this.key(viewType, document.uri);
 		if (this._documents.has(key)) {
-			throw new Error(`Document already exists for viewType:${document.viewType} resource:${document.uri}`);
+			throw new Error(`Document already exists for viewType:${viewType} resource:${document.uri}`);
 		}
 		this._documents.set(key, document);
 	}
 
-	public delete(document: extHostTypes.CustomDocument) {
-		const key = this.key(document.viewType, document.uri);
+	public delete(viewType: string, document: extHostTypes.CustomDocument) {
+		const key = this.key(viewType, document.uri);
 		this._documents.delete(key);
 	}
 
@@ -414,7 +414,7 @@ export class ExtHostWebviews implements extHostProtocol.ExtHostWebviewsShape {
 				disposables.add(provider.editingDelegate.onDidEdit(e => {
 					const document = e.document;
 					const editId = (document as extHostTypes.CustomDocument)._addEdit(e.edit);
-					this._proxy.$onDidEdit(document.uri, document.viewType, editId, e.label);
+					this._proxy.$onDidEdit(document.uri, viewType, editId, e.label);
 				}));
 			}
 		}
@@ -516,7 +516,7 @@ export class ExtHostWebviews implements extHostProtocol.ExtHostWebviewsShape {
 
 		const revivedResource = URI.revive(resource);
 		const document = await entry.provider.openCustomDocument(revivedResource, cancellation);
-		this._documents.add(document as extHostTypes.CustomDocument);
+		this._documents.add(viewType, document as extHostTypes.CustomDocument);
 		return {
 			editable: !!entry.provider.editingDelegate,
 		};
@@ -534,7 +534,7 @@ export class ExtHostWebviews implements extHostProtocol.ExtHostWebviewsShape {
 
 		const revivedResource = URI.revive(resource);
 		const document = this.getCustomDocument(viewType, revivedResource);
-		this._documents.delete(document);
+		this._documents.delete(viewType, document);
 		document._dispose();
 	}