diff --git a/ManagedCode.Database.Cosmos/CosmosItem.cs b/ManagedCode.Database.Cosmos/CosmosItem.cs
index 9195e05..8b8b873 100644
--- a/ManagedCode.Database.Cosmos/CosmosItem.cs
+++ b/ManagedCode.Database.Cosmos/CosmosItem.cs
@@ -21,7 +21,7 @@ public CosmosItem(string id)
 
     [JsonProperty("type")] public string Type { get; set; }
 
-    public virtual PartitionKey PartitionKey => new(Id);
+    public PartitionKey PartitionKey { get; protected set; }
 
     [JsonProperty("id")] public string Id { get; set; }
 }
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