diff --git a/src/ReC.Client/ReCClient.cs b/src/ReC.Client/ReCClient.cs
index c985668..923e5ac 100644
--- a/src/ReC.Client/ReCClient.cs
+++ b/src/ReC.Client/ReCClient.cs
@@ -33,7 +33,11 @@ namespace ReC.Client
             _http = httpClientFactory.CreateClient(ClientName);
         }
 
+#if NETFRAMEWORK
         private static string BuildQuery(params (string Key, object Value)[] parameters)
+#else
+        private static string BuildQuery(params (string Key, object? Value)[] parameters)
+#endif
         {
             var parts = parameters
                 .Where(p => p.Value != null)