diff --git a/src/MultipartStreamBuilder.php b/src/MultipartStreamBuilder.php
index 72d35f2..4280552 100644
--- a/src/MultipartStreamBuilder.php
+++ b/src/MultipartStreamBuilder.php
@@ -122,7 +122,7 @@ private function prepareHeaders($name, StreamInterface $stream, $filename, array
         if (!$this->hasHeader($headers, 'content-disposition')) {
             $headers['Content-Disposition'] = sprintf('form-data; name="%s"', $name);
             if ($hasFilename) {
-                $headers['Content-Disposition'] .= sprintf('; filename="%s"', basename($filename));
+                $headers['Content-Disposition'] .= sprintf('; filename="%s"', pathinfo($filename, PATHINFO_BASENAME));
             }
         }