diff --git a/backend/user/api/serializer.py b/backend/user/api/serializer.py
index a16477a..ebae601 100644
--- a/backend/user/api/serializer.py
+++ b/backend/user/api/serializer.py
@@ -166,6 +166,7 @@ def deep_merge(base, overrides):
     'burn_days_yellow': 10,
     'burn_resupply_days': 18,
     'burn_origin': 'Antares Station Warehouse',
+    'supply_cart_days': 20,
     'layout_navigation_style': 'full',
     'plan_overrides': {},
 }
@@ -190,6 +191,7 @@ class UserPreferenceSerializer(JSONSafeSerializerMixin, serializers.Serializer):
     burnDaysYellow = serializers.IntegerField(source='burn_days_yellow', min_value=0, default=10, required=False)
     burnResupplyDays = serializers.IntegerField(source='burn_resupply_days', min_value=0, default=18, required=False)
     burnOrigin = serializers.CharField(source='burn_origin', required=False)
+    supplyCartDays = serializers.IntegerField(source='supply_cart_days', min_value=0, default=20, required=False)
     layoutNavigationStyle = serializers.CharField(source='layout_navigation_style', required=False)
 
     planOverrides = serializers.DictField(