diff --git a/types/ecore/index.d.ts b/types/ecore/index.d.ts
index 0fd9325f0f..863aae9aef 100644
--- a/types/ecore/index.d.ts
+++ b/types/ecore/index.d.ts
@@ -117,7 +117,7 @@ export interface Resource extends EObject {
     clear: () => EList;
     each: (iterator: (value: any, key: any, list: EList) => void, context?: any) => void;
     save: (callback: () => void, options: any) => void;
-    parse: (data: EObject, loader: () => void) => any;
+    parse: (data: EObject, loader?: () => void) => any;
     remove: () => void;
     rev: string;
     load: (res: any) => void;