diff --git a/api/advent22_api/routers/_security.py b/api/advent22_api/routers/_security.py
index 29f406a..1e548fe 100644
--- a/api/advent22_api/routers/_security.py
+++ b/api/advent22_api/routers/_security.py
@@ -57,7 +57,7 @@ async def user_can_view_day(
     True iff das Türchen von Tag `day` user-sichtbar ist
     """
 
-    if day < 0:
+    if day < 1:
         raise HTTPException(status.HTTP_422_UNPROCESSABLE_ENTITY)
 
-    return day < await user_visible_doors()
+    return day <= await user_visible_doors()