diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 03f995b..d0b9045 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -2,35 +2,32 @@ name: CI
 
 on:
   pull_request:
-      branches:
-        - main
+    branches:
+      - main
   push:
-      branches:
-        - main
+    branches:
+      - main
   merge_group: {}
 
 jobs:
-  test:
-    name: test & typecheck
+  ci:
+    name: Build, Typecheck & Test
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repo
         uses: actions/checkout@v4
 
-      - uses: pnpm/action-setup@v4
-        name: Install pnpm
-        with:
-          version: 9
-          run_install: false
+      - name: Install pnpm
+        uses: pnpm/action-setup@v4
 
       - name: Install Node.js
         uses: actions/setup-node@v4
         with:
           node-version: 20
-          cache: 'pnpm'
+          cache: pnpm
 
       - name: Install dependencies
-        run: pnpm install
+        run: pnpm install --frozen-lockfile
 
       - name: Build
         run: pnpm build
diff --git a/packages/better-fetch/src/utils.ts b/packages/better-fetch/src/utils.ts
index fb05686..6b7e1f4 100644
--- a/packages/better-fetch/src/utils.ts
+++ b/packages/better-fetch/src/utils.ts
@@ -105,17 +105,12 @@ export async function getHeaders(opts?: BetterFetchOption) {
 	const headers = new Headers();
 	
 	if (opts?.headers) {
-		if (opts.headers instanceof Headers) {
-			opts.headers.forEach((value, key) => {
-				headers.set(key, value);
-			});
-		} else {
-			for (const [key, value] of Object.entries(opts.headers)) {
-				if (value !== null && value !== undefined) {
-					headers.set(key, value);
-				}
-			}
-		}
+		const source = opts.headers instanceof Headers
+			? opts.headers
+			: new Headers(opts.headers as HeadersInit);
+		source.forEach((value, key) => {
+			headers.set(key, value);
+		});
 	}
 	
 	const authHeader = await getAuthHeader(opts);
@@ -212,18 +207,13 @@ export function getBody(options?: BetterFetchOption) {
 	if (!options?.body) {
 		return null;
 	}
-	
-	let hasContentType = false;
-	if (options?.headers) {
-		if (options.headers instanceof Headers) {
-			hasContentType = options.headers.has("content-type");
-		} else if (typeof options.headers === "object") {
-			hasContentType = "content-type" in options.headers && 
-				options.headers["content-type"] !== null && 
-				options.headers["content-type"] !== undefined;
-		}
-	}
-	
+
+	const headers = options?.headers
+		? new Headers(options.headers as HeadersInit)
+		: null;
+
+	const hasContentType = headers?.has("content-type") ?? false;
+
 	if (isJSONSerializable(options.body) && !hasContentType) {
 		for (const [key, value] of Object.entries(options?.body)) {
 			if (value instanceof Date) {
@@ -233,10 +223,7 @@ export function getBody(options?: BetterFetchOption) {
 		return JSON.stringify(options.body);
 	}
 
-	if (
-		headers.has("content-type") &&
-		headers.get("content-type") === "application/x-www-form-urlencoded"
-	) {
+	if (headers?.get("content-type") === "application/x-www-form-urlencoded") {
 		if (isJSONSerializable(options.body)) {
 			return new URLSearchParams(options.body).toString();
 		}