Get opening post only once when reversing post url

boards/models/post.py

@@ -318,10 +318,11 b' class Post(models.Model):'
         link = cache.get(cache_key)
 
         if not link:
-            if not self.is_opening():
-                link = reverse('thread', kwargs={
-                    'post_id': self.thread_new.get_opening_post().id}) + '#' + str(
-                    self.id)
+            opening_post = self.thread_new.get_opening_post()
+            if self == opening_post:
+                link = reverse('thread',
+                        kwargs={'post_id': opening_post.id}) + '#' + str(
+                                self.id)
             else:
                 link = reverse('thread', kwargs={'post_id': self.id})