diff --git a/src/vs/vscode.d.ts b/src/vs/vscode.d.ts
index 7cbf36df53e..a1c0eab3e2c 100644
--- a/src/vs/vscode.d.ts
+++ b/src/vs/vscode.d.ts
@@ -112,10 +112,16 @@ declare module 'vscode' {
 		readonly version: number;
 
 		/**
-		 * true if there are unpersisted changes.
+		 * `true` if there are unpersisted changes.
 		 */
 		readonly isDirty: boolean;
 
+		/**
+		 * `true` if the document have been closed. A closed document isn't synchronized anymore
+		 * and won't be re-used when the same resource is opened again.
+		 */
+		readonly isClosed: boolean;
+
 		/**
 		 * Save the underlying file.
 		 *
diff --git a/src/vs/workbench/api/node/extHostDocumentData.ts b/src/vs/workbench/api/node/extHostDocumentData.ts
index ee8d0bc2d8d..c8777b54fed 100644
--- a/src/vs/workbench/api/node/extHostDocumentData.ts
+++ b/src/vs/workbench/api/node/extHostDocumentData.ts
@@ -72,6 +72,7 @@ export class ExtHostDocumentData extends MirrorModel2 {
 				get isUntitled() { return data._uri.scheme !== 'file'; },
 				get languageId() { return data._languageId; },
 				get version() { return data._versionId; },
+				get isClosed() { return data._isDisposed; },
 				get isDirty() { return data._isDirty; },
 				save() { return data._save(); },
 				getText(range?) { return range ? data._getTextInRange(range) : data.getText(); },