diff --git a/lib/utils.js b/lib/utils.js
index 852ee97..8ee2955 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -41,20 +41,20 @@ async function * intoAsyncIterator (payload) {
   const isBuffer = Buffer.isBuffer(payload)
 
   if (
-    (
+    !isBuffer && (
     // ArrayBuffer
       payload instanceof ArrayBuffer ||
     // NodeJS.TypedArray
     ArrayBuffer.isView(payload)
-    ) &&
-    // Exclude Buffer to prevent double cast
-    !isBuffer
+    )
   ) {
     payload = Buffer.from(payload)
   }
 
+  const isObject = typeof payload === 'object'
+
   // Iterator
-  if (typeof payload === 'object' && typeof payload[Symbol.iterator] === 'function' && !isBuffer) {
+  if (!isBuffer && isObject && Symbol.iterator in payload) {
     for (const chunk of payload) {
       yield chunk
     }
@@ -62,7 +62,7 @@ async function * intoAsyncIterator (payload) {
   }
 
   // Async Iterator
-  if (typeof payload === 'object' && typeof payload[Symbol.asyncIterator] === 'function' && !isBuffer) {
+  if (!isBuffer && isObject && Symbol.asyncIterator in payload) {
     for await (const chunk of payload) {
       yield chunk
     }