diff --git a/test/netstd/Client/Client.csproj b/test/netstd/Client/Client.csproj
index 828ea73..d3504d4 100644
--- a/test/netstd/Client/Client.csproj
+++ b/test/netstd/Client/Client.csproj
@@ -20,6 +20,7 @@
 
   <PropertyGroup>
     <TargetFramework>net5.0</TargetFramework>
+    <LangVersion>9.0</LangVersion>
     <AssemblyName>Client</AssemblyName>
     <PackageId>Client</PackageId>
     <OutputType>Exe</OutputType>