diff --git a/src/file.ts b/src/file.ts
index 3525dfdea..f765a7296 100644
--- a/src/file.ts
+++ b/src/file.ts
@@ -472,7 +472,7 @@ export interface FileMetadata extends BaseMetadata {
   md5Hash?: string;
   mediaLink?: string;
   metadata?: {
-    [key: string]: string;
+    [key: string]: string | boolean | number | null;
   };
   metageneration?: string | number;
   name?: string;