diff --git a/types/jsonapi-serializer/index.d.ts b/types/jsonapi-serializer/index.d.ts
index 4d9344bc28..2368981378 100644
--- a/types/jsonapi-serializer/index.d.ts
+++ b/types/jsonapi-serializer/index.d.ts
@@ -29,7 +29,7 @@ export interface SerializerOptions {
     pluralizeType?: boolean;
     typeForAttribute?: TypeForAttribute;
     meta?: object;
-    transform?: (() => void);
+    transform?: Transform;
 }
 
 export interface KeyForAttribute {