diff --git a/doc/Usage.md b/doc/Usage.md
index 398c243c..0abbbf00 100644
--- a/doc/Usage.md
+++ b/doc/Usage.md
@@ -224,6 +224,10 @@ $pages = $pdf->getPages();
 $mediaBox = [];
 foreach ($pages as $page) {
     $details = $page->getDetails();
+    // The page could haven't the Mediabox, then we get this information from document
+    if (!isset($details['MediaBox'])) {
+        $details = reset($pdf->getObjectsByType('Pages'))->getHeader()->getDetails();
+    }
     $mediaBox[] = [
         'width' => $details['MediaBox'][2],
         'height' => $details['MediaBox'][3]