diff --git a/lib/_http_outgoing.js b/lib/_http_outgoing.js
index 7ac93bd3d8f498..f097bd4c8413e4 100644
--- a/lib/_http_outgoing.js
+++ b/lib/_http_outgoing.js
@@ -876,16 +876,15 @@ function write_(msg, chunk, encoding, callback, fromEnd) {
     return false;
   }
 
-  let len = msg.strictContentLength ?
-    typeof chunk === 'string' ? Buffer.byteLength(chunk, encoding) : chunk.byteLength : null;
+  let len;
 
-  if (len != null) {
-    if (
-      strictContentLength(msg) &&
-      (fromEnd ? msg[kBytesWritten] + len !== msg._contentLength : msg[kBytesWritten] + len > msg._contentLength)
-    ) {
+  if (strictContentLength(msg)) {
+    len ??= typeof chunk === 'string' ? Buffer.byteLength(chunk, encoding) : chunk.byteLength;
+
+    if (fromEnd ? msg[kBytesWritten] + len !== msg._contentLength : msg[kBytesWritten] + len > msg._contentLength) {
       throw new ERR_HTTP_CONTENT_LENGTH_MISMATCH(len + msg[kBytesWritten], msg._contentLength);
     }
+
     msg[kBytesWritten] += len;
   }