diff --git a/src/Http/CurlDispatcher.php b/src/Http/CurlDispatcher.php
index ac989973..259a9df4 100644
--- a/src/Http/CurlDispatcher.php
+++ b/src/Http/CurlDispatcher.php
@@ -210,7 +210,7 @@ private function writeBody($curl, $string): int
         }
 
         if ($this->body->getSize() > self::$contentLengthThreshold) {
-            return count($string);
+            return strlen($string);
         }
 
         return $this->body->write($string);