diff --git a/test/netstd/Server/Server.csproj b/test/netstd/Server/Server.csproj
index fe1c394..e2ec93c 100644
--- a/test/netstd/Server/Server.csproj
+++ b/test/netstd/Server/Server.csproj
@@ -20,6 +20,7 @@
 
   <PropertyGroup>
     <TargetFramework>net5.0</TargetFramework>
+    <LangVersion>9.0</LangVersion>
     <AssemblyName>Server</AssemblyName>
     <PackageId>Server</PackageId>
     <OutputType>Exe</OutputType>