diff --git a/program/serializers.py b/program/serializers.py
index e9481b51e98b1e21286d2a00ee5fbee7366fbc7f..24d20e62b5b60bd21be565cde4432467f2fa5739 100644
--- a/program/serializers.py
+++ b/program/serializers.py
@@ -1038,7 +1038,7 @@ class TimeSlotSerializer(serializers.ModelSerializer):
     def to_representation(self, instance):
         representation = super().to_representation(instance)
 
-        if not self.context.get("request").user.is_authenticated:
+        if not (self.context.get("request") and self.context.get("request").user.is_authenticated):
             del representation["memo"]
 
         return representation