diff --git a/Common/Brokerages/TastytradeBrokerageModel.cs b/Common/Brokerages/TastytradeBrokerageModel.cs
index cd81bc786d52..8671a9d11e92 100644
--- a/Common/Brokerages/TastytradeBrokerageModel.cs
+++ b/Common/Brokerages/TastytradeBrokerageModel.cs
@@ -55,7 +55,7 @@ public class TastytradeBrokerageModel : DefaultBrokerageModel
         /// <summary>
         /// The set of <see cref="OrderType"/> values that cannot be used for cross-zero execution.
         /// </summary>
-        private static IReadOnlySet<OrderType> NotSupportedCrossZeroOrderTypes => new HashSet<OrderType>()
+        private static readonly IReadOnlySet<OrderType> NotSupportedCrossZeroOrderTypes = new HashSet<OrderType>()
         {
             OrderType.ComboLimit
         };
diff --git a/Common/Brokerages/TradeStationBrokerageModel.cs b/Common/Brokerages/TradeStationBrokerageModel.cs
index 30309319b0d9..51e4fe5139e4 100644
--- a/Common/Brokerages/TradeStationBrokerageModel.cs
+++ b/Common/Brokerages/TradeStationBrokerageModel.cs
@@ -75,7 +75,7 @@ public class TradeStationBrokerageModel : DefaultBrokerageModel
         /// <summary>
         /// The set of <see cref="OrderType"/> values that cannot be used for cross-zero execution.
         /// </summary>
-        private static IReadOnlySet<OrderType> NotSupportedCrossZeroOrderTypes => new HashSet<OrderType>()
+        private static readonly IReadOnlySet<OrderType> NotSupportedCrossZeroOrderTypes = new HashSet<OrderType>()
         {
             OrderType.ComboMarket,
             OrderType.ComboLimit,