1 files changed, 3 insertions, 1 deletions
diff --git a/comments.py b/comments.py
index 2fa66e6..dc56594 100644
--- a/comments.py
+++ b/comments.py
@@ -158,7 +158,9 @@ class CommentedBase(object):
         return getattr(self, Comment.attrib)
 
     def yaml_end_comment_extend(self, comment, clear=False):
-        if clear:
+        if comment is None:
+            return
+        if clear or self.ca.end is None:
             self.ca.end = []
         self.ca.end.extend(comment)