diff --git a/integration-tests/typescript-axios/src/audit-github-repositories.ts b/integration-tests/typescript-axios/src/audit-github-repositories.ts
index 4c7bfd60..9a283473 100644
--- a/integration-tests/typescript-axios/src/audit-github-repositories.ts
+++ b/integration-tests/typescript-axios/src/audit-github-repositories.ts
@@ -15,7 +15,6 @@ const client = new ApiClient({
   }),
   basePath: GitHubV3RestApiServers.default(),
   defaultTimeout: 5_000,
-  defaultHeaders: {},
 })
 
 async function main() {
diff --git a/integration-tests/typescript-axios/src/uniform-github-repositories.ts b/integration-tests/typescript-axios/src/uniform-github-repositories.ts
index aba416f3..af7502cd 100644
--- a/integration-tests/typescript-axios/src/uniform-github-repositories.ts
+++ b/integration-tests/typescript-axios/src/uniform-github-repositories.ts
@@ -12,7 +12,6 @@ const client = new ApiClient({
   }),
   basePath: "https://api.github.com",
   defaultTimeout: 5_000,
-  defaultHeaders: {},
 })
 
 async function main() {
diff --git a/packages/typescript-axios-runtime/src/main.ts b/packages/typescript-axios-runtime/src/main.ts
index 1a6163cd..03087d23 100644
--- a/packages/typescript-axios-runtime/src/main.ts
+++ b/packages/typescript-axios-runtime/src/main.ts
@@ -60,7 +60,7 @@ export type Server<T> = string & {__server__: T}
 export interface AbstractAxiosConfig {
   axios?: AxiosInstance
   basePath: string
-  defaultHeaders: Record<string, string>
+  defaultHeaders?: Record<string, string>
   defaultTimeout?: number
 }
 
@@ -73,7 +73,7 @@ export abstract class AbstractAxiosClient {
   protected constructor(config: AbstractAxiosConfig) {
     this.axios = config.axios ?? axios
     this.basePath = config.basePath
-    this.defaultHeaders = config.defaultHeaders
+    this.defaultHeaders = config.defaultHeaders ?? {}
     this.defaultTimeout = config.defaultTimeout
   }
 
diff --git a/packages/typescript-fetch-runtime/src/main.ts b/packages/typescript-fetch-runtime/src/main.ts
index 03abddd7..452a0727 100644
--- a/packages/typescript-fetch-runtime/src/main.ts
+++ b/packages/typescript-fetch-runtime/src/main.ts
@@ -39,7 +39,7 @@ export type Server<T> = string & {__server__: T}
 
 export interface AbstractFetchClientConfig {
   basePath: string
-  defaultHeaders: Record<string, string>
+  defaultHeaders?: Record<string, string>
   defaultTimeout?: number
 }
 
@@ -75,7 +75,7 @@ export abstract class AbstractFetchClient {
 
   protected constructor(config: AbstractFetchClientConfig) {
     this.basePath = config.basePath
-    this.defaultHeaders = config.defaultHeaders
+    this.defaultHeaders = config.defaultHeaders ?? {}
     this.defaultTimeout = config.defaultTimeout
   }