diff --git a/src/PhpSpreadsheet/Writer/Pdf/Dompdf.php b/src/PhpSpreadsheet/Writer/Pdf/Dompdf.php
index 9ae2ccee35..87e8eeb5f6 100644
--- a/src/PhpSpreadsheet/Writer/Pdf/Dompdf.php
+++ b/src/PhpSpreadsheet/Writer/Pdf/Dompdf.php
@@ -59,7 +59,7 @@ public function save($pFilename): void
 
         //  Create PDF
         $pdf = $this->createExternalWriterInstance();
-        $pdf->setPaper(strtolower($paperSize), $orientation);
+        $pdf->setPaper($paperSize, $orientation);
 
         $pdf->loadHtml($this->generateHTMLAll());
         $pdf->render();
diff --git a/src/PhpSpreadsheet/Writer/Pdf/Mpdf.php b/src/PhpSpreadsheet/Writer/Pdf/Mpdf.php
index 75e0010d5f..56ac693066 100644
--- a/src/PhpSpreadsheet/Writer/Pdf/Mpdf.php
+++ b/src/PhpSpreadsheet/Writer/Pdf/Mpdf.php
@@ -64,7 +64,7 @@ public function save($pFilename): void
         $config = ['tempDir' => $this->tempDir . '/mpdf'];
         $pdf = $this->createExternalWriterInstance($config);
         $ortmp = $orientation;
-        $pdf->_setPageSize(strtoupper($paperSize), $ortmp);
+        $pdf->_setPageSize($paperSize, $ortmp);
         $pdf->DefOrientation = $orientation;
         $pdf->AddPageByArray([
             'orientation' => $orientation,