diff --git a/DotNetSolutionTools.Photino/DotNetSolutionTools.Photino.csproj b/DotNetSolutionTools.Photino/DotNetSolutionTools.Photino.csproj
index cda34c6..6da65d7 100644
--- a/DotNetSolutionTools.Photino/DotNetSolutionTools.Photino.csproj
+++ b/DotNetSolutionTools.Photino/DotNetSolutionTools.Photino.csproj
@@ -17,6 +17,7 @@
 	</ItemGroup>
 
 	<ItemGroup>
+		<PackageReference Include="Ardalis.GuardClauses" Version="5.0.0" />
 		<PackageReference Include="MudBlazor" Version="8.6.0" />
 		<PackageReference Include="Photino.Blazor" Version="4.0.13" />
 		<PackageReference Include="Z.Blazor.Diagrams" Version="3.0.3" />
diff --git a/DotNetSolutionTools.Photino/Models/AppState.cs b/DotNetSolutionTools.Photino/Models/AppState.cs
index 0faee31..4f61170 100644
--- a/DotNetSolutionTools.Photino/Models/AppState.cs
+++ b/DotNetSolutionTools.Photino/Models/AppState.cs
@@ -2,7 +2,7 @@
 
 public class AppState
 {
-    public required string SolutionFolderPath { get; set; }
-    public required string SolutionFilePath { get; set; }
-    public required string CsprojFilePath { get; set; }
+    public required string? SolutionFolderPath { get; set; }
+    public required string? SolutionFilePath { get; set; }
+    public required string? CsprojFilePath { get; set; }
 }
diff --git a/DotNetSolutionTools.Photino/Pages/Home.razor b/DotNetSolutionTools.Photino/Pages/Home.razor
index 7df5955..5b5bdcd 100644
--- a/DotNetSolutionTools.Photino/Pages/Home.razor
+++ b/DotNetSolutionTools.Photino/Pages/Home.razor
@@ -1,4 +1,5 @@
 @page "/"
+@using Ardalis.GuardClauses
 @using DotNetSolutionTools.Core
 @using DotNetSolutionTools.Core.Models
 @using DotNetSolutionTools.Photino.Models
@@ -29,6 +30,7 @@
 
     private void Populate()
     {
+        Guard.Against.Null(_solutionFilePath);
         var result = SolutionBuildOrder.GetBuildOrder(_solutionFilePath);
         _projects = result;
     }