diff --git a/packages/fetch/src/index.ts b/packages/fetch/src/index.ts
index cbc165775..9881186b5 100644
--- a/packages/fetch/src/index.ts
+++ b/packages/fetch/src/index.ts
@@ -142,7 +142,7 @@ ${
   const ignoreContentTypes = ['multipart/form-data'];
   const fetchHeadersOption =
     body.contentType && !ignoreContentTypes.includes(body.contentType)
-      ? `headers: { 'Content-Type': '${body.contentType}' }`
+      ? `headers: { 'Content-Type': '${body.contentType}', ...options?.headers }`
       : '';
   const requestBodyParams = generateBodyOptions(
     body,
diff --git a/samples/hono/hono-with-fetch-client/next-app/app/gen/pets/pets.ts b/samples/hono/hono-with-fetch-client/next-app/app/gen/pets/pets.ts
index 7c7f6f05e..931632850 100644
--- a/samples/hono/hono-with-fetch-client/next-app/app/gen/pets/pets.ts
+++ b/samples/hono/hono-with-fetch-client/next-app/app/gen/pets/pets.ts
@@ -65,7 +65,7 @@ export const createPets = async (
   const res = await fetch(getCreatePetsUrl(), {
     ...options,
     method: 'POST',
-    headers: { 'Content-Type': 'application/json' },
+    headers: { 'Content-Type': 'application/json', ...options?.headers },
     body: JSON.stringify(createPetsBodyItem),
   });
   const data = await res.json();
@@ -92,7 +92,7 @@ export const updatePets = async (
   const res = await fetch(getUpdatePetsUrl(), {
     ...options,
     method: 'PUT',
-    headers: { 'Content-Type': 'application/json' },
+    headers: { 'Content-Type': 'application/json', ...options?.headers },
     body: JSON.stringify(pet),
   });
   const data = await res.json();
diff --git a/samples/next-app-with-fetch/app/gen/pets/pets.ts b/samples/next-app-with-fetch/app/gen/pets/pets.ts
index 4bf681042..5eae12873 100644
--- a/samples/next-app-with-fetch/app/gen/pets/pets.ts
+++ b/samples/next-app-with-fetch/app/gen/pets/pets.ts
@@ -91,7 +91,7 @@ export const createPets = async (
   return customFetch<Promise<createPetsResponse>>(getCreatePetsUrl(), {
     ...options,
     method: 'POST',
-    headers: { 'Content-Type': 'application/json' },
+    headers: { 'Content-Type': 'application/json', ...options?.headers },
     body: JSON.stringify(createPetsBodyItem),
   });
 };
@@ -115,7 +115,7 @@ export const updatePets = async (
   return customFetch<Promise<updatePetsResponse>>(getUpdatePetsUrl(), {
     ...options,
     method: 'PUT',
-    headers: { 'Content-Type': 'application/json' },
+    headers: { 'Content-Type': 'application/json', ...options?.headers },
     body: JSON.stringify(pet),
   });
 };
diff --git a/samples/react-app-with-swr/fetch-client/src/api/endpoints/swaggerPetstore.ts b/samples/react-app-with-swr/fetch-client/src/api/endpoints/swaggerPetstore.ts
index f3d6702a0..4f932f3dd 100644
--- a/samples/react-app-with-swr/fetch-client/src/api/endpoints/swaggerPetstore.ts
+++ b/samples/react-app-with-swr/fetch-client/src/api/endpoints/swaggerPetstore.ts
@@ -100,7 +100,7 @@ export const createPets = async (
   const res = await fetch(getCreatePetsUrl(), {
     ...options,
     method: 'POST',
-    headers: { 'Content-Type': 'application/json' },
+    headers: { 'Content-Type': 'application/json', ...options?.headers },
     body: JSON.stringify(createPetsBody),
   });
   const data = await res.json();
diff --git a/samples/react-query/custom-fetch/src/gen/pets/pets.ts b/samples/react-query/custom-fetch/src/gen/pets/pets.ts
index 70d7ba252..3d0be3196 100644
--- a/samples/react-query/custom-fetch/src/gen/pets/pets.ts
+++ b/samples/react-query/custom-fetch/src/gen/pets/pets.ts
@@ -222,7 +222,7 @@ export const createPets = async (
   return customFetch<Promise<createPetsResponse>>(getCreatePetsUrl(), {
     ...options,
     method: 'POST',
-    headers: { 'Content-Type': 'application/json' },
+    headers: { 'Content-Type': 'application/json', ...options?.headers },
     body: JSON.stringify(createPetsBodyItem),
   });
 };
@@ -304,7 +304,7 @@ export const updatePets = async (
   return customFetch<Promise<updatePetsResponse>>(getUpdatePetsUrl(), {
     ...options,
     method: 'PUT',
-    headers: { 'Content-Type': 'application/json' },
+    headers: { 'Content-Type': 'application/json', ...options?.headers },
     body: JSON.stringify(pet),
   });
 };
diff --git a/samples/svelte-query/custom-fetch/src/gen/pets/pets.ts b/samples/svelte-query/custom-fetch/src/gen/pets/pets.ts
index e00db3d81..7dc7cb04c 100644
--- a/samples/svelte-query/custom-fetch/src/gen/pets/pets.ts
+++ b/samples/svelte-query/custom-fetch/src/gen/pets/pets.ts
@@ -172,7 +172,7 @@ export const createPets = async (
   return customFetch<Promise<createPetsResponse>>(getCreatePetsUrl(), {
     ...options,
     method: 'POST',
-    headers: { 'Content-Type': 'application/json' },
+    headers: { 'Content-Type': 'application/json', ...options?.headers },
     body: JSON.stringify(createPetsBodyItem),
   });
 };
@@ -254,7 +254,7 @@ export const updatePets = async (
   return customFetch<Promise<updatePetsResponse>>(getUpdatePetsUrl(), {
     ...options,
     method: 'PUT',
-    headers: { 'Content-Type': 'application/json' },
+    headers: { 'Content-Type': 'application/json', ...options?.headers },
     body: JSON.stringify(pet),
   });
 };
diff --git a/samples/swr-with-zod/src/gen/endpoints/pets/pets.ts b/samples/swr-with-zod/src/gen/endpoints/pets/pets.ts
index fa5ddf410..bd60cca43 100644
--- a/samples/swr-with-zod/src/gen/endpoints/pets/pets.ts
+++ b/samples/swr-with-zod/src/gen/endpoints/pets/pets.ts
@@ -137,7 +137,7 @@ export const createPets = async (
   const res = await fetch(getCreatePetsUrl(), {
     ...options,
     method: 'POST',
-    headers: { 'Content-Type': 'application/json' },
+    headers: { 'Content-Type': 'application/json', ...options?.headers },
     body: JSON.stringify(createPetsBodyItem),
   });
   const data = await res.json();
@@ -205,7 +205,7 @@ export const updatePets = async (
   const res = await fetch(getUpdatePetsUrl(), {
     ...options,
     method: 'PUT',
-    headers: { 'Content-Type': 'application/json' },
+    headers: { 'Content-Type': 'application/json', ...options?.headers },
     body: JSON.stringify(pet),
   });
   const data = await res.json();
diff --git a/samples/vue-query/custom-fetch/src/gen/pets/pets.ts b/samples/vue-query/custom-fetch/src/gen/pets/pets.ts
index 1639e6326..1b3394331 100644
--- a/samples/vue-query/custom-fetch/src/gen/pets/pets.ts
+++ b/samples/vue-query/custom-fetch/src/gen/pets/pets.ts
@@ -174,7 +174,7 @@ export const createPets = async (
   return customFetch<Promise<createPetsResponse>>(getCreatePetsUrl(), {
     ...options,
     method: 'POST',
-    headers: { 'Content-Type': 'application/json' },
+    headers: { 'Content-Type': 'application/json', ...options?.headers },
     body: JSON.stringify(createPetsBodyItem),
   });
 };
@@ -256,7 +256,7 @@ export const updatePets = async (
   return customFetch<Promise<updatePetsResponse>>(getUpdatePetsUrl(), {
     ...options,
     method: 'PUT',
-    headers: { 'Content-Type': 'application/json' },
+    headers: { 'Content-Type': 'application/json', ...options?.headers },
     body: JSON.stringify(pet),
   });
 };