diff --git a/musicmetadata/musicmetadata.d.ts b/musicmetadata/musicmetadata.d.ts
index b772468546..0e951f8d08 100644
--- a/musicmetadata/musicmetadata.d.ts
+++ b/musicmetadata/musicmetadata.d.ts
@@ -19,8 +19,8 @@ declare module "musicmetadata" {
 
 declare namespace MM {
     export interface Options {
-        duration: boolean;
-        fileSize: number;
+        duration?: boolean;
+        fileSize?: number;
     }
 
     export interface Metadata {
@@ -45,4 +45,4 @@ declare namespace MM {
         format: string;
         data: Buffer;
     }
-}
\ No newline at end of file
+}