diff --git a/Libraries/LibWeb/HTML/HTMLSelectElement.cpp b/Libraries/LibWeb/HTML/HTMLSelectElement.cpp
index 424fe131041..a99d4da9fb1 100644
--- a/Libraries/LibWeb/HTML/HTMLSelectElement.cpp
+++ b/Libraries/LibWeb/HTML/HTMLSelectElement.cpp
@@ -203,18 +203,19 @@ Vector<GC::Root<HTMLOptionElement>> HTMLSelectElement::list_of_options() const
     // and all the option element children of all the optgroup element children of the select element, in tree order.
     Vector<GC::Root<HTMLOptionElement>> list;
 
-    for_each_child_of_type<HTMLOptionElement>([&](HTMLOptionElement& option_element) {
-        list.append(GC::make_root(option_element));
-        return IterationDecision::Continue;
-    });
+    for (auto* node = first_child(); node; node = node->next_sibling()) {
+        if (auto* maybe_option = as_if<HTMLOptionElement>(*node)) {
+            list.append(GC::make_root(const_cast<HTMLOptionElement&>(*maybe_option)));
+            continue;
+        }
 
-    for_each_child_of_type<HTMLOptGroupElement>([&](HTMLOptGroupElement const& optgroup_element) {
-        optgroup_element.for_each_child_of_type<HTMLOptionElement>([&](HTMLOptionElement& option_element) {
-            list.append(GC::make_root(option_element));
-            return IterationDecision::Continue;
-        });
-        return IterationDecision::Continue;
-    });
+        if (auto* maybe_opt_group = as_if<HTMLOptGroupElement>(node)) {
+            maybe_opt_group->for_each_child_of_type<HTMLOptionElement>([&](HTMLOptionElement& option_element) {
+                list.append(GC::make_root(option_element));
+                return IterationDecision::Continue;
+            });
+        }
+    }
 
     return list;
 }
diff --git a/Tests/LibWeb/Text/expected/HTML/select-index-is-in-tree-order.txt b/Tests/LibWeb/Text/expected/HTML/select-index-is-in-tree-order.txt
new file mode 100644
index 00000000000..00750edc07d
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/HTML/select-index-is-in-tree-order.txt
@@ -0,0 +1 @@
+3
diff --git a/Tests/LibWeb/Text/input/HTML/select-index-is-in-tree-order.html b/Tests/LibWeb/Text/input/HTML/select-index-is-in-tree-order.html
new file mode 100644
index 00000000000..88188698ec3
--- /dev/null
+++ b/Tests/LibWeb/Text/input/HTML/select-index-is-in-tree-order.html
@@ -0,0 +1,16 @@
+<select id="test-select">
+    <option value="0" selected>Option 0</option>
+    <optgroup label="Group 1">
+        <option value="1">Option 1</option>
+        <option value="2">Option 2</option>
+    </optgroup>
+    <option value="3" selected>Option 3</option>
+    <option value="4">Option 4</option>
+</select>
+<script src="../include.js"></script>
+<script>
+    test(() => {
+        const selectElement = document.getElementById('test-select');
+        println(selectElement.selectedIndex);
+    });
+</script>