diff --git a/ServiceScan.SourceGenerator.Tests/AddServicesTests.cs b/ServiceScan.SourceGenerator.Tests/AddServicesTests.cs
index a9872d8..2c8e67b 100644
--- a/ServiceScan.SourceGenerator.Tests/AddServicesTests.cs
+++ b/ServiceScan.SourceGenerator.Tests/AddServicesTests.cs
@@ -956,6 +956,7 @@ public class MyService2 : IService { }
             public class ParentType2
             {
                 public class MyService1 : IService { }
+                private class NestedPrivateService : IService { } // Shouldn't be added as non-accessible
             }
             """);
 
diff --git a/ServiceScan.SourceGenerator.Tests/TestServices.cs b/ServiceScan.SourceGenerator.Tests/TestServices.cs
index 4c0ce85..4987319 100644
--- a/ServiceScan.SourceGenerator.Tests/TestServices.cs
+++ b/ServiceScan.SourceGenerator.Tests/TestServices.cs
@@ -3,3 +3,6 @@
 public interface IExternalService;
 public class ExternalService1 : IExternalService { }
 public class ExternalService2 : IExternalService { }
+
+// Shouldn't be added as type is not accessible from other assembly
+internal class InternalExternalService2 : IExternalService { }
\ No newline at end of file
diff --git a/ServiceScan.SourceGenerator/DependencyInjectionGenerator.FilterTypes.cs b/ServiceScan.SourceGenerator/DependencyInjectionGenerator.FilterTypes.cs
index 65960a0..2543d77 100644
--- a/ServiceScan.SourceGenerator/DependencyInjectionGenerator.FilterTypes.cs
+++ b/ServiceScan.SourceGenerator/DependencyInjectionGenerator.FilterTypes.cs
@@ -13,6 +13,9 @@ public partial class DependencyInjectionGenerator
     private static IEnumerable<(INamedTypeSymbol Type, INamedTypeSymbol[]? MatchedAssignableTypes)> FilterTypes
         (Compilation compilation, AttributeModel attribute, INamedTypeSymbol containingType)
     {
+        var semanticModel = compilation.GetSemanticModel(attribute.Location.SourceTree);
+        var position = attribute.Location.SourceSpan.Start;
+
         var assemblies = GetAssembliesToScan(compilation, attribute, containingType);
 
         var assignableToType = attribute.AssignableToTypeName is null
@@ -76,6 +79,9 @@ public partial class DependencyInjectionGenerator
             if (assignableToType != null && !IsAssignableTo(type, assignableToType, out matchedTypes))
                 continue;
 
+            if (!semanticModel.IsAccessible(position, type))
+                continue;
+
             yield return (type, matchedTypes);
         }
     }
diff --git a/ServiceScan.SourceGenerator/DependencyInjectionGenerator.cs b/ServiceScan.SourceGenerator/DependencyInjectionGenerator.cs
index 0d46ef6..0ac50ee 100644
--- a/ServiceScan.SourceGenerator/DependencyInjectionGenerator.cs
+++ b/ServiceScan.SourceGenerator/DependencyInjectionGenerator.cs
@@ -15,11 +15,11 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
     {
         context.RegisterPostInitializationOutput(context =>
         {
-            context.AddSource("ServiceScanAttributes.Generated.cs", SourceText.From(GenerateAttributeSource.Source, Encoding.UTF8));
+            context.AddSource("ServiceScanAttributes.Generated.cs", SourceText.From(GenerateAttributeInfo.Source, Encoding.UTF8));
         });
 
         var methodProvider = context.SyntaxProvider.ForAttributeWithMetadataName(
-                "ServiceScan.SourceGenerator.GenerateServiceRegistrationsAttribute",
+                GenerateAttributeInfo.MetadataName,
                 predicate: static (syntaxNode, ct) => syntaxNode is MethodDeclarationSyntax methodSyntax,
                 transform: static (context, ct) => ParseRegisterMethodModel(context))
             .Where(method => method != null);
diff --git a/ServiceScan.SourceGenerator/GenerateAttributeSource.cs b/ServiceScan.SourceGenerator/GenerateAttributeInfo.cs
similarity index 96%
rename from ServiceScan.SourceGenerator/GenerateAttributeSource.cs
rename to ServiceScan.SourceGenerator/GenerateAttributeInfo.cs
index d288f44..0d7a719 100644
--- a/ServiceScan.SourceGenerator/GenerateAttributeSource.cs
+++ b/ServiceScan.SourceGenerator/GenerateAttributeInfo.cs
@@ -1,8 +1,10 @@
 namespace ServiceScan.SourceGenerator;
 
-internal static class GenerateAttributeSource
+internal static class GenerateAttributeInfo
 {
-    public static string Source => """
+    public const string MetadataName = "ServiceScan.SourceGenerator.GenerateServiceRegistrationsAttribute";
+
+    public const string Source = """
         #nullable enable
 
         using System;