diff --git a/src/OutlookAddin/OutlookAddin.csproj b/src/OutlookAddin/OutlookAddin.csproj
index 3ae8686..ab10460 100644
--- a/src/OutlookAddin/OutlookAddin.csproj
+++ b/src/OutlookAddin/OutlookAddin.csproj
@@ -28,6 +28,8 @@
     <AssemblyName>MarcusLaw.OutlookAddin</AssemblyName>
     <LoadBehavior>3</LoadBehavior>
     <TargetFrameworkVersion>v4.8</TargetFrameworkVersion>
+    <LangVersion>latest</LangVersion>
+    <Nullable>enable</Nullable>
     <DefineConstants>VSTO40;UseOfficeInterop</DefineConstants>
     <BootstrapperEnabled>true</BootstrapperEnabled>
     <BootstrapperComponentsLocation>HomeSite</BootstrapperComponentsLocation>