diff --git a/src/constants.ts b/src/constants.ts
index dd0a0be..aca50ce 100644
--- a/src/constants.ts
+++ b/src/constants.ts
@@ -14,6 +14,5 @@ export const CANCELLED_ERROR = 'CanceledError';
 
 export const GET = 'GET';
 export const POST = 'POST';
-export const PUT = 'PUT';
 export const DELETE = 'DELETE';
 export const HEAD = 'HEAD';
diff --git a/src/request-handler.ts b/src/request-handler.ts
index 4e67b41..59f5c53 100644
--- a/src/request-handler.ts
+++ b/src/request-handler.ts
@@ -40,11 +40,9 @@ import {
   CANCELLED_ERROR,
   CHARSET_UTF_8,
   CONTENT_TYPE,
-  DELETE,
   GET,
   HEAD,
   OBJECT,
-  PUT,
   STRING,
   UNDEFINED,
 } from './constants';
@@ -180,23 +178,25 @@ export function createRequestHandler(
     method: string,
     body?: unknown,
   ): void => {
-    if (!body && [PUT, DELETE].includes(method)) {
+    if (!body && ['PUT', 'DELETE'].includes(method)) {
       return;
-    }
-
-    const contentTypeValue = APPLICATION_JSON + ';' + CHARSET_UTF_8;
+    } else {
+      const contentTypeValue = APPLICATION_JSON + ';' + CHARSET_UTF_8;
 
-    if (headers instanceof Headers) {
-      if (!headers.has(CONTENT_TYPE)) {
-        headers.set(CONTENT_TYPE, contentTypeValue);
+      if (headers instanceof Headers) {
+        if (!headers.has(CONTENT_TYPE)) {
+          headers.set(CONTENT_TYPE, contentTypeValue);
+        }
+      } else if (
+        typeof headers === OBJECT &&
+        !Array.isArray(headers) &&
+        !headers[CONTENT_TYPE]
+      ) {
+        headers[CONTENT_TYPE] = contentTypeValue;
       }
-    } else if (
-      typeof headers === OBJECT &&
-      !Array.isArray(headers) &&
-      !headers[CONTENT_TYPE]
-    ) {
-      headers[CONTENT_TYPE] = contentTypeValue;
     }
+
+    return;
   };
 
   /**
diff --git a/test/request-handler.spec.ts b/test/request-handler.spec.ts
index d1c18c0..787b74a 100644
--- a/test/request-handler.spec.ts
+++ b/test/request-handler.spec.ts
@@ -13,10 +13,8 @@ import {
   APPLICATION_JSON,
   CHARSET_UTF_8,
   CONTENT_TYPE,
-  DELETE,
   GET,
   POST,
-  PUT,
 } from '../src/constants';
 import { ResponseErr } from '../src/response-error';
 
@@ -295,10 +293,10 @@ describe('Request Handler', () => {
     });
 
     describe.each([
-      { method: DELETE, body: undefined, expectContentType: false },
-      { method: PUT, body: undefined, expectContentType: false },
-      { method: DELETE, body: { foo: 'bar' }, expectContentType: true },
-      { method: PUT, body: { foo: 'bar' }, expectContentType: true },
+      { method: 'DELETE', body: undefined, expectContentType: false },
+      { method: 'PUT', body: undefined, expectContentType: false },
+      { method: 'DELETE', body: { foo: 'bar' }, expectContentType: true },
+      { method: 'PUT', body: { foo: 'bar' }, expectContentType: true },
       { method: POST, body: undefined, expectContentType: true },
       { method: GET, body: undefined, expectContentType: true },
     ])(
@@ -323,7 +321,7 @@ describe('Request Handler', () => {
       },
     );
 
-    describe.each([DELETE, PUT])(
+    describe.each(['DELETE', 'PUT'])(
       '%s method with custom Content-Type',
       (method) => {
         it(`should keep custom Content-Type for ${method} method`, () => {