diff --git a/src/vs/monaco.d.ts b/src/vs/monaco.d.ts
index 075f07e4f3006722a275095690a2079c6e3f93fc..44b859b748a7dd1998984db2b2019a35d93b45ab 100644
--- a/src/vs/monaco.d.ts
+++ b/src/vs/monaco.d.ts
@@ -1993,8 +1993,8 @@ declare namespace monaco.editor {
 	 * (Serializable) View state for the diff editor.
 	 */
 	export interface IDiffEditorViewState {
-		original: ICodeEditorViewState;
-		modified: ICodeEditorViewState;
+		original: ICodeEditorViewState | null;
+		modified: ICodeEditorViewState | null;
 	}
 
 	/**