diff --git a/Services/LocationService.cs b/Services/LocationService.cs
index 730b996..017203d 100644
--- a/Services/LocationService.cs
+++ b/Services/LocationService.cs
@@ -64,7 +64,8 @@ public class LocationService
         var idFilter = Builders<Location>.Filter.Eq(l => l.Id, locationId);
 
         // if the Content array is null, initialize it first
-        var nullFilter = idFilter & Builders<Location>.Filter.Eq("Content", BsonNull.Value);
+        // use a raw BsonDocument filter to avoid casting BsonNull to an ObjectId
+        var nullFilter = idFilter & new BsonDocument("Content", BsonNull.Value);
         var initArray = Builders<Location>.Update.Set(l => l.Content, new List<string>());
         await _locations.UpdateOneAsync(nullFilter, initArray);
 
@@ -77,7 +78,8 @@ public class LocationService
         if (!ObjectId.TryParse(locationId, out _) || !ObjectId.TryParse(itemId, out _))
             return;
 
-        var filter = Builders<Location>.Filter.Eq(l => l.Id, locationId) & Builders<Location>.Filter.Ne("Content", BsonNull.Value);
+        // check that the Content array exists by using a raw BsonDocument filter
+        var filter = Builders<Location>.Filter.Eq(l => l.Id, locationId) & new BsonDocument("Content", new BsonDocument("$ne", BsonNull.Value));
         var update = Builders<Location>.Update.Pull(l => l.Content, itemId);
         await _locations.UpdateOneAsync(filter, update);
     }