diff --git a/src/Spout/Writer/Internal/XLSX/Workbook.php b/src/Spout/Writer/Internal/XLSX/Workbook.php
index 1c521ea..83f17b0 100644
--- a/src/Spout/Writer/Internal/XLSX/Workbook.php
+++ b/src/Spout/Writer/Internal/XLSX/Workbook.php
@@ -132,7 +132,7 @@ class Workbook
      * @param Worksheet $worksheet
      * @return void
      */
-    public function setCurrentWorksheet($worksheet)
+    protected function setCurrentWorksheet($worksheet)
     {
         $this->currentWorksheet = $worksheet;
     }