diff --git a/fet2020/posts/models.py b/fet2020/posts/models.py
index 9e5fb270..2d1d791f 100644
--- a/fet2020/posts/models.py
+++ b/fet2020/posts/models.py
@@ -197,28 +197,68 @@ class Post(models.Model):
         )
         return value
 
-    @property
-    def agenda_url(self):
-        if self.has_agenda:
-            return ep_get_url(self.agenda_key)
-        return "#"
+    _agenda_filename = None
+    _agenda_url = "#"
 
     @property
-    def protocol_url(self):
-        if self.has_protocol:
-            return ep_get_url(self.protocol_key)
-        return "#"
+    def agenda_url(self):
+        if self.has_agenda is not True:
+            self.a_url = "#"
+            self._agenda_filename = None
+            return self.a_url
+
+        if self._agenda_url != "#":
+            return self._agenda_url
+
+        if (url := ep_get_url(self.agenda_key)) != "#":
+            self._agenda_url = url
+            self._agenda_filename = self.slug + "-agenda.pdf"
+        else:
+            self._agenda_url = "#"
+            self._agenda_filename = None
+
+        return self._agenda_url
 
     @property
     def agenda_filename(self):
+        if self._agenda_filename is not None:
+            return self._agenda_filename
+
         if self.has_agenda and self.agenda_url != "#":
             return self.slug + "-agenda.pdf"
+
         return None
 
+    _protocol_filename = None
+    _protocol_url = "#"
+
+    @property
+    def protocol_url(self):
+        if self.has_protocol is not True:
+            self._protocol_url = "#"
+            self._protocol_filename = None
+            return self._protocol_url
+
+        if self._protocol_url != "#":
+            return self._protocol_url
+
+        if (url := ep_get_url(self.protocol_key)) != "#":
+            self._protocol_url = url
+            self._protocol_filename = self.slug + "-agenda.pdf"
+        else:
+            self._protocol_url = "#"
+            self._protocol_filename = None
+
+        return self._protocol_url
+
     @property
     def protocol_filename(self):
+        if self._protocol_filename is not None:
+            return self._protocol_filename
+
         if self.has_protocol and self.protocol_url != "#":
             return self.slug + "-protokoll.pdf"
+
         return None
 
     def create_agenda_key(self):