diff --git a/markdownify/__init__.py b/markdownify/__init__.py
index 7d14fe7..8f72773 100644
--- a/markdownify/__init__.py
+++ b/markdownify/__init__.py
@@ -444,7 +444,7 @@ def convert_li(self, el, text, convert_as_inline):
                 start = int(parent.get("start"))
             else:
                 start = 1
-            bullet = '%s.' % (start + parent.index(el))
+            bullet = '%s.' % (start + len(el.find_previous_siblings('li')))
         else:
             depth = -1
             while el:
diff --git a/tests/test_lists.py b/tests/test_lists.py
index 6b320ca..e9480ab 100644
--- a/tests/test_lists.py
+++ b/tests/test_lists.py
@@ -42,6 +42,7 @@
 
 def test_ol():
     assert md('<ol><li>a</li><li>b</li></ol>') == '\n\n1. a\n2. b\n'
+    assert md('<ol><!--comment--><li>a</li><span/><li>b</li></ol>') == '\n\n1. a\n2. b\n'
     assert md('<ol start="3"><li>a</li><li>b</li></ol>') == '\n\n3. a\n4. b\n'
     assert md('foo<ol start="3"><li>a</li><li>b</li></ol>bar') == 'foo\n\n3. a\n4. b\n\nbar'
     assert md('<ol start="-1"><li>a</li><li>b</li></ol>') == '\n\n1. a\n2. b\n'