diff --git a/src/Chapter05.Tests/Listing05.12.PassingCommandLineArgumentsToMain.Tests.cs b/src/Chapter05.Tests/Listing05.12.PassingCommandLineArgumentsToMain.Tests.cs
index 8f4e7222c..13a3a42cd 100644
--- a/src/Chapter05.Tests/Listing05.12.PassingCommandLineArgumentsToMain.Tests.cs
+++ b/src/Chapter05.Tests/Listing05.12.PassingCommandLineArgumentsToMain.Tests.cs
@@ -31,7 +31,7 @@ public void Main_GoodArgs_DownloadFile()
             {
                 Assert.AreEqual(0, Program.Main(args));
             }
-            catch (AggregateException exception) when(exception.InnerException.GetType() == typeof(System.Net.Http.HttpRequestException))
+            catch (AggregateException exception) when(exception.InnerException?.GetType() == typeof(System.Net.Http.HttpRequestException))
             {
                 Assert.Inconclusive("Unable to download the file.  Check your Internet connection.");
             }
diff --git a/src/Shared/NetCore.cs b/src/Shared/NetCore.cs
index 440fbe376..4fac3bf0d 100644
--- a/src/Shared/NetCore.cs
+++ b/src/Shared/NetCore.cs
@@ -1,15 +1,16 @@
-using System;
-using System.Reflection;
-
-public class NetCore
-{
-    public static string GetNetCoreVersion()
-    {
-        var assembly = typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly;
-        var assemblyPath = assembly.CodeBase.Split(new[] { '/', '\\' }, StringSplitOptions.RemoveEmptyEntries);
-        int netCoreAppIndex = Array.IndexOf(assemblyPath, "Microsoft.NETCore.App");
-        if (netCoreAppIndex > 0 && netCoreAppIndex < assemblyPath.Length - 2)
-            return assemblyPath[netCoreAppIndex + 1];
-        throw new Exception("Unable to determine .NET Core version.");
-    }
-}
+using System;
+using System.Reflection;
+
+public class NetCore
+{
+    public static string GetNetCoreVersion()
+    {
+        Assembly assembly = typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly;
+        var assemblyCodeBase = assembly.CodeBase ?? throw new ArgumentNullException("assemblyCodeBase");
+        string[] assemblyPath = assemblyCodeBase.Split(new[] { '/', '\\' }, StringSplitOptions.RemoveEmptyEntries);
+        int netCoreAppIndex = Array.IndexOf(assemblyPath, "Microsoft.NETCore.App");
+        if (netCoreAppIndex > 0 && netCoreAppIndex < assemblyPath.Length - 2)
+            return assemblyPath[netCoreAppIndex + 1];
+        throw new Exception("Unable to determine .NET Core version.");
+    }
+}