diff --git a/ArchiSteamFarm/ArchiWebHandler.cs b/ArchiSteamFarm/ArchiWebHandler.cs
index d05d947a7..388e2641a 100644
--- a/ArchiSteamFarm/ArchiWebHandler.cs
+++ b/ArchiSteamFarm/ArchiWebHandler.cs
@@ -190,7 +190,7 @@ namespace ArchiSteamFarm {
 						asset.Rarity = description.Rarity;
 
 						if (description.AdditionalProperties != null) {
-							asset.AdditionalProperties = description.AdditionalProperties.ToImmutableDictionary();
+							asset.AdditionalProperties = description.AdditionalProperties;
 						}
 
 						assetIDs.Add(asset.AssetID);
diff --git a/ArchiSteamFarm/Json/Steam.cs b/ArchiSteamFarm/Json/Steam.cs
index c97365898..3c85d2301 100644
--- a/ArchiSteamFarm/Json/Steam.cs
+++ b/ArchiSteamFarm/Json/Steam.cs
@@ -42,7 +42,7 @@ namespace ArchiSteamFarm.Json {
 
 			[JsonIgnore]
 			[PublicAPI]
-			public ImmutableDictionary<string, JToken>? AdditionalProperties { get; internal set; }
+			public IReadOnlyDictionary<string, JToken>? AdditionalPropertiesReadOnly => AdditionalProperties;
 
 			[JsonIgnore]
 			[PublicAPI]
@@ -91,6 +91,9 @@ namespace ArchiSteamFarm.Json {
 			[PublicAPI]
 			public EType Type { get; internal set; }
 
+			[JsonExtensionData]
+			internal Dictionary<string, JToken>? AdditionalProperties { private get; set; }
+
 #pragma warning disable IDE0051
 			[JsonProperty(PropertyName = "amount", Required = Required.Always)]
 			private string AmountText {