diff --git a/src/Workleap.Extensions.MediatR.Analyzers/Internals/KnownSymbolNames.cs b/src/Workleap.Extensions.MediatR.Analyzers/Internals/KnownSymbolNames.cs
index b61e0d5..25f6ec4 100644
--- a/src/Workleap.Extensions.MediatR.Analyzers/Internals/KnownSymbolNames.cs
+++ b/src/Workleap.Extensions.MediatR.Analyzers/Internals/KnownSymbolNames.cs
@@ -1,4 +1,4 @@
-namespace Workleap.Extensions.MediatR.Analyzers.Internals;
+namespace Workleap.Extensions.MediatR.Analyzers.Internals;
 
 internal static class KnownSymbolNames
 {
@@ -8,7 +8,8 @@ internal static class KnownSymbolNames
     public const string WorkleapExtMediatRAssembly = "Workleap.Extensions.MediatR";
 
     public const string ServiceCollectionInterface = "Microsoft.Extensions.DependencyInjection.IServiceCollection";
-    public const string ServiceCollectionExtensionsClass = "Microsoft.Extensions.DependencyInjection.ServiceCollectionExtensions";
+    public const string MediatROldServiceCollectionExtensionsClass = "Microsoft.Extensions.DependencyInjection.ServiceCollectionExtensions";
+    public const string MediatRServiceCollectionExtensionsClass = "Microsoft.Extensions.DependencyInjection.MediatRServiceCollectionExtensions";
     public const string WorkleapMediatorExtensionsClass = "MediatR.MediatorExtensions";
 
     public const string BaseRequestInterface = "MediatR.IBaseRequest";
diff --git a/src/Workleap.Extensions.MediatR.Analyzers/ServiceRegistrationAnalyzer.cs b/src/Workleap.Extensions.MediatR.Analyzers/ServiceRegistrationAnalyzer.cs
index fcb8387..6334f1f 100644
--- a/src/Workleap.Extensions.MediatR.Analyzers/ServiceRegistrationAnalyzer.cs
+++ b/src/Workleap.Extensions.MediatR.Analyzers/ServiceRegistrationAnalyzer.cs
@@ -1,4 +1,4 @@
-using System.Collections.Immutable;
+using System.Collections.Immutable;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.Operations;
@@ -44,7 +44,11 @@ private sealed class AnalyzerImplementation
         public AnalyzerImplementation(Compilation compilation)
         {
             this._serviceCollectionType = compilation.GetBestTypeByMetadataName(KnownSymbolNames.ServiceCollectionInterface, KnownSymbolNames.MsExtDIAbstractionsAssembly)!;
-            this._serviceCollectionExtensionsType = compilation.GetBestTypeByMetadataName(KnownSymbolNames.ServiceCollectionExtensionsClass, KnownSymbolNames.MediatRAssembly)!;
+
+            // Class name changed in MediatR 13.1, this is for backward compatibility
+            this._serviceCollectionExtensionsType =
+                compilation.GetBestTypeByMetadataName(KnownSymbolNames.MediatRServiceCollectionExtensionsClass, KnownSymbolNames.MediatRAssembly) ??
+                compilation.GetBestTypeByMetadataName(KnownSymbolNames.MediatROldServiceCollectionExtensionsClass, KnownSymbolNames.MediatRAssembly)!;
         }
 
         public bool IsValid => this._serviceCollectionExtensionsType != null;
diff --git a/src/Workleap.Extensions.MediatR.Tests/HostBuilderTests.cs b/src/Workleap.Extensions.MediatR.Tests/HostBuilderTests.cs
index ae942e9..5cf8ba0 100644
--- a/src/Workleap.Extensions.MediatR.Tests/HostBuilderTests.cs
+++ b/src/Workleap.Extensions.MediatR.Tests/HostBuilderTests.cs
@@ -3,6 +3,7 @@
 using Microsoft.AspNetCore.Builder;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 
 namespace Workleap.Extensions.MediatR.Tests;
 public sealed class HostBuilderTests
@@ -11,6 +12,12 @@ public sealed class HostBuilderTests
     public async Task SetLicenseFromConfiguration()
     {
         var builder = WebApplication.CreateBuilder();
+        builder.Host.UseDefaultServiceProvider(options =>
+        {
+            // Disabling build on validation since some private classes (like TestState) are not registered
+            options.ValidateOnBuild = false;
+        });
+
         builder.Services.AddMediator(typeof(HostBuilderTests).Assembly);
         builder.Configuration.AddInMemoryCollection([KeyValuePair.Create<string, string?>("MEDIATR_LICENSE_KEY", "License")]);