diff --git a/lib/core/util.js b/lib/core/util.js
index 76714f61d32..2bad24df2f6 100644
--- a/lib/core/util.js
+++ b/lib/core/util.js
@@ -212,7 +212,7 @@ function bodyLength (body) {
       : null
   } else if (isBlobLike(body)) {
     return body.size != null ? body.size : null
-  } else if (Buffer.isBuffer(body)) {
+  } else if (isBuffer(body)) {
     return body.byteLength
   }
 
@@ -341,10 +341,12 @@ function parseRawHeaders (headers) {
 
   return ret
 }
+
 function isBuffer (buffer) {
   // See, https://github.com/mcollina/undici/pull/319
   return buffer instanceof Uint8Array || Buffer.isBuffer(buffer)
 }
+
 function validateHandler (handler, method, upgrade) {
   if (!handler || typeof handler !== 'object') {
     throw new InvalidArgumentError('handler must be an object')