diff --git a/index.d.ts b/index.d.ts
index c193d1d664..3be6df6f5b 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1,5 +1,5 @@
 // TypeScript Version: 4.1
-type AxiosHeaderValue = string | string[] | number | boolean | null;
+type AxiosHeaderValue = AxiosHeaders | string | string[] | number | boolean | null;
 type RawAxiosHeaders = Record<string, AxiosHeaderValue>;
 
 type MethodsHeaders = {