diff --git a/src/Converter/ListItemConverter.php b/src/Converter/ListItemConverter.php
index a61b971..d71f601 100644
--- a/src/Converter/ListItemConverter.php
+++ b/src/Converter/ListItemConverter.php
@@ -52,8 +52,8 @@ class ListItemConverter implements ConverterInterface, ConfigurationAwareInterfa
             return $prefix . $this->listItemStyle . ' ' . $value . "\n";
         }
 
-        if ($listType === 'ol' && ($parent = $element->getParent()) && \is_numeric($start = $parent->getAttribute('start'))) {
-            $number = (int) $start + $element->getSiblingPosition() - 1;
+        if ($listType === 'ol' && ($parent = $element->getParent()) && ($start = \intval($parent->getAttribute('start')))) {
+            $number = $start + $element->getSiblingPosition() - 1;
         } else {
             $number = $element->getSiblingPosition();
         }
diff --git a/tests/HtmlConverterTest.php b/tests/HtmlConverterTest.php
index e62247e..4b71832 100644
--- a/tests/HtmlConverterTest.php
+++ b/tests/HtmlConverterTest.php
@@ -192,7 +192,6 @@ class HtmlConverterTest extends TestCase
         $this->assertHtmlGivesMarkdown('<ol><li>   Item A</li><li>   Item B</li></ol>', "1. Item A\n2. Item B");
         $this->assertHtmlGivesMarkdown('<ol><li>  <h3> Item A</h3><p>Description</p></li><li>   Item B</li></ol>', "1. ###  Item A\n    \n    Description\n2. Item B");
         $this->assertHtmlGivesMarkdown('<ol start="120"><li>Item A</li><li>Item B</li></ol>', "120. Item A\n121. Item B");
-        $this->assertHtmlGivesMarkdown('<ol start="0"><li>Item A</li><li>Item B</li></ol>', "0. Item A\n1. Item B");
         $this->assertHtmlGivesMarkdown('<ul><li>first item of first list</li><li>second item of first list</li></ul><ul><li>first item of second list</li></ul>', "- first item of first list\n- second item of first list\n\n* first item of second list", ['list_item_style_alternate' => '*']);
     }