diff --git a/tools/Directory.Build.props b/tools/Directory.Build.props
index b933b03..39e3440 100644
--- a/tools/Directory.Build.props
+++ b/tools/Directory.Build.props
@@ -1,6 +1,7 @@
 <Project>
     <PropertyGroup>
         <LangVersion>11.0</LangVersion>
+        <Nullable>enable</Nullable>
         <ImplicitUsings>true</ImplicitUsings>
         <ExcludeFromCodeCoverage>true</ExcludeFromCodeCoverage>
         <PackageLicenseFile/>