diff --git a/tests/FilterLists.Agent.Tests/Extensions/ReadOnlyListExtensionsTests.cs b/tests/FilterLists.Agent.Tests/Extensions/ReadOnlyListExtensionsTests.cs
index 737ab8a3c..0dadc40ee 100644
--- a/tests/FilterLists.Agent.Tests/Extensions/ReadOnlyListExtensionsTests.cs
+++ b/tests/FilterLists.Agent.Tests/Extensions/ReadOnlyListExtensionsTests.cs
@@ -1,5 +1,4 @@
-using System;
-using System.Collections.Generic;
+using System.Collections.Generic;
 using FilterLists.Agent.Extensions;
 using Xunit;
 
@@ -7,13 +6,6 @@ namespace FilterLists.Agent.Tests.Extensions
 {
     public class ReadOnlyListExtensionsTests
     {
-        [Fact]
-        public void FirstOrDefault_WithNullParameter_ThrowsArgumentNullException()
-        {
-            var list = (IReadOnlyList<int>)null;
-            Assert.Throws<ArgumentNullException>(() => list.FirstOrDefault());
-        }
-
         [Fact]
         public void FirstOrDefault_WithEmptyList_ReturnsDefault()
         {
diff --git a/tests/FilterLists.Agent.Tests/FilterLists.Agent.Tests.csproj b/tests/FilterLists.Agent.Tests/FilterLists.Agent.Tests.csproj
index a2e89e56e..61fdb1720 100644
--- a/tests/FilterLists.Agent.Tests/FilterLists.Agent.Tests.csproj
+++ b/tests/FilterLists.Agent.Tests/FilterLists.Agent.Tests.csproj
@@ -3,7 +3,9 @@
   <PropertyGroup>
     <TargetFramework>netcoreapp2.2</TargetFramework>
     <TargetLatestRuntimePatch>true</TargetLatestRuntimePatch>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>8.0</LangVersion>
+    <Nullable>enable</Nullable>
+    <NullableContextOptions>enable</NullableContextOptions>
     <Authors>Collin M. Barrett</Authors>
     <Company>Collin M. Barrett</Company>
     <Product>FilterLists</Product>