diff --git a/index.d.cts b/index.d.cts
index 8d133e9fe2..6f07d1aec0 100644
--- a/index.d.cts
+++ b/index.d.cts
@@ -8,6 +8,8 @@ type MethodsHeaders = Partial<{
 
 type AxiosHeaderMatcher = (this: AxiosHeaders, value: string, name: string, headers: RawAxiosHeaders) => boolean;
 
+type AxiosHeaderParser = (this: AxiosHeaders, value: axios.AxiosHeaderValue, header: string) => any;
+
 type CommonRequestHeadersList = 'Accept' | 'Content-Length' | 'User-Agent'| 'Content-Encoding' | 'Authorization';
 
 type ContentType = axios.AxiosHeaderValue | 'text/html' | 'text/plain' | 'multipart/form-data' | 'application/json' | 'application/x-www-form-urlencoded' | 'application/octet-stream';
@@ -16,18 +18,18 @@ type CommonResponseHeadersList = 'Server' | 'Content-Type' | 'Content-Length' |
 
 declare class AxiosHeaders {
   constructor(
-      headers?: RawAxiosHeaders | AxiosHeaders
+      headers?: RawAxiosHeaders | AxiosHeaders | string
   );
 
   [key: string]: any;
 
   set(headerName?: string, value?: axios.AxiosHeaderValue, rewrite?: boolean | AxiosHeaderMatcher): AxiosHeaders;
-  set(headers?: RawAxiosHeaders | AxiosHeaders, rewrite?: boolean): AxiosHeaders;
+  set(headers?: RawAxiosHeaders | AxiosHeaders | string, rewrite?: boolean): AxiosHeaders;
 
   get(headerName: string, parser: RegExp): RegExpExecArray | null;
-  get(headerName: string, matcher?: true | AxiosHeaderMatcher): axios.AxiosHeaderValue;
+  get(headerName: string, matcher?: true | AxiosHeaderParser): axios.AxiosHeaderValue;
 
-  has(header: string, matcher?: true | AxiosHeaderMatcher): boolean;
+  has(header: string, matcher?: AxiosHeaderMatcher): boolean;
 
   delete(header: string | string[], matcher?: AxiosHeaderMatcher): boolean;
 
diff --git a/index.d.ts b/index.d.ts
index 19a7d1a91f..79cdd800c9 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -9,22 +9,24 @@ type MethodsHeaders = Partial<{
   [Key in Method as Lowercase<Key>]: AxiosHeaders;
 } & {common: AxiosHeaders}>;
 
-type AxiosHeaderMatcher = (this: AxiosHeaders, value: string, name: string, headers: RawAxiosHeaders) => boolean;
+type AxiosHeaderMatcher = string | RegExp | ((this: AxiosHeaders, value: string, name: string) => boolean);
+
+type AxiosHeaderParser = (this: AxiosHeaders, value: AxiosHeaderValue, header: string) => any;
 
 export class AxiosHeaders {
   constructor(
-      headers?: RawAxiosHeaders | AxiosHeaders
+      headers?: RawAxiosHeaders | AxiosHeaders | string
   );
 
   [key: string]: any;
 
   set(headerName?: string, value?: AxiosHeaderValue, rewrite?: boolean | AxiosHeaderMatcher): AxiosHeaders;
-  set(headers?: RawAxiosHeaders | AxiosHeaders, rewrite?: boolean): AxiosHeaders;
+  set(headers?: RawAxiosHeaders | AxiosHeaders | string, rewrite?: boolean): AxiosHeaders;
 
   get(headerName: string, parser: RegExp): RegExpExecArray | null;
-  get(headerName: string, matcher?: true | AxiosHeaderMatcher): AxiosHeaderValue;
+  get(headerName: string, matcher?: true | AxiosHeaderParser): AxiosHeaderValue;
 
-  has(header: string, matcher?: true | AxiosHeaderMatcher): boolean;
+  has(header: string, matcher?: AxiosHeaderMatcher): boolean;
 
   delete(header: string | string[], matcher?: AxiosHeaderMatcher): boolean;