diff --git a/index.d.ts b/index.d.ts
index 71a05df1ee98693d882864686e9264484441e13f..08842113a6fdf06b3f201647b34539897d147c76 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1,5 +1,5 @@
 export interface AxiosTransformer {
-  (data: any): any;
+  (data: any, headers?: any): any;
 }
 
 export interface AxiosAdapter {