diff --git a/src/context.ts b/src/context.ts
index b46783df1..f4a29674c 100644
--- a/src/context.ts
+++ b/src/context.ts
@@ -307,9 +307,10 @@ type ResponseHeader =
   | 'X-Robots-Tag'
   | 'X-XSS-Protection'
 
-interface SetHeaders {
+interface SetHeaders<E extends Env> {
   (name: 'Content-Type', value?: BaseMime, options?: SetHeadersOptions): void
   (name: ResponseHeader, value?: string, options?: SetHeadersOptions): void
+  (name: NonNullable<E['Headers']>, value?: string, options?: SetHeadersOptions): void
   (name: string, value?: string, options?: SetHeadersOptions): void
 }
 
@@ -576,7 +577,7 @@ export class Context<
    * })
    * ```
    */
-  header: SetHeaders = (name, value, options): void => {
+  header: SetHeaders<E> = (name, value, options): void => {
     // Clear the header
     if (value === undefined) {
       if (this.#headers) {
diff --git a/src/types.ts b/src/types.ts
index e5b240034..82b9cfb66 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -25,11 +25,13 @@ import type {
 
 export type Bindings = object
 export type Variables = object
+export type CustomHeaders = string
 
 export type BlankEnv = {}
 export type Env = {
   Bindings?: Bindings
   Variables?: Variables
+  Headers?: CustomHeaders
 }
 
 export type Next = () => Promise<void>