diff --git a/src/vs/workbench/api/electron-browser/mainThreadEditors.ts b/src/vs/workbench/api/electron-browser/mainThreadEditors.ts
index b55e298c67f..8d464d9e0ba 100644
--- a/src/vs/workbench/api/electron-browser/mainThreadEditors.ts
+++ b/src/vs/workbench/api/electron-browser/mainThreadEditors.ts
@@ -164,7 +164,7 @@ export class MainThreadEditors implements MainThreadEditorsShape {
 
 	$trySetDecorations(id: string, key: string, ranges: IDecorationOptions[]): TPromise<any> {
 		if (!this._documentsAndEditors.getEditor(id)) {
-			return TPromise.as(null);
+			return TPromise.wrapError(new Error('TextEditor disposed'));
 		}
 		this._documentsAndEditors.getEditor(id).setDecorations(key, ranges);
 		return TPromise.as(null);