diff --git a/.gitignore b/.gitignore
index 10e12b3..a9f796b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,6 +5,7 @@
 
 # dotenv files
 .env
+*.lscache
 
 # User-specific files
 *.rsuser
diff --git a/src/CarpaNet.SourceGen/CarpaNet.SourceGen.csproj b/src/CarpaNet.SourceGen/CarpaNet.SourceGen.csproj
index 857b26a..fb9a026 100644
--- a/src/CarpaNet.SourceGen/CarpaNet.SourceGen.csproj
+++ b/src/CarpaNet.SourceGen/CarpaNet.SourceGen.csproj
@@ -11,6 +11,10 @@
     <IsPackable>false</IsPackable>
   </PropertyGroup>
 
+  <ItemGroup>
+    <InternalsVisibleTo Include="CarpaNet.UnitTests, PublicKey=00240000048000009400000006020000002400005253413100040000010001005311bd88d09f39da8d0a7814421594e8769c2c6af9b162a58a5c531868178ee6f8c3a108ffef4035eebe195bc06615043564b1c319b5b83be9ee8fae7f99a5b0b52cab19f8aabb66acbe9384dfda7a5d359e6b34ac3f7907db45f2c0c33c2bb4290ca55adc414a1823888a92d9b9f61c32f48d391be17000f3032e0b5146b48b" />
+  </ItemGroup>
+
   <ItemGroup>
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp" PrivateAssets="all" />
     <PackageReference Include="System.Text.Json" PrivateAssets="all" GeneratePathProperty="true" />
diff --git a/src/CarpaNet.SourceGen/Generation/JsonContextGenerator.cs b/src/CarpaNet.SourceGen/Generation/JsonContextGenerator.cs
index c3b4a98..d1509b3 100644
--- a/src/CarpaNet.SourceGen/Generation/JsonContextGenerator.cs
+++ b/src/CarpaNet.SourceGen/Generation/JsonContextGenerator.cs
@@ -799,7 +799,7 @@ private static void GenerateListTypeFactory(
         dispatchLines.Add($"if (type == typeof({globalList})) return Create_BuiltIn_{safeName}_TypeInfo(options);");
     }
 
-    private static string ToBuiltInSuffix(string typeName)
+    internal static string ToBuiltInSuffix(string typeName)
     {
         return typeName switch
         {
@@ -809,7 +809,7 @@ private static string ToBuiltInSuffix(string typeName)
             "int" => "Int32",
             "byte[]" => "ByteArray",
             "object" => "Object",
-            _ => typeName.Replace(".", "_").Replace("@", "")
+            _ => typeName.Replace(".", "_").Replace("@", "").Replace("<", "_").Replace(">", "_")
         };
     }
 }
diff --git a/tests/CarpaNet.UnitTests/Generation/JsonContextGeneratorTests.cs b/tests/CarpaNet.UnitTests/Generation/JsonContextGeneratorTests.cs
new file mode 100644
index 0000000..5ebd401
--- /dev/null
+++ b/tests/CarpaNet.UnitTests/Generation/JsonContextGeneratorTests.cs
@@ -0,0 +1,33 @@
+using CarpaNet.Generation;
+
+using Xunit;
+
+namespace CarpaNet.UnitTests.Generation;
+
+public class JsonContextGeneratorTests
+{
+    [Theory]
+    [InlineData("string", "String")]
+    [InlineData("long", "Int64")]
+    [InlineData("bool", "Boolean")]
+    [InlineData("int", "Int32")]
+    [InlineData("byte[]", "ByteArray")]
+    [InlineData("object", "Object")]
+    [InlineData("System.DateTimeOffset", "System_DateTimeOffset")]
+    [InlineData("System.Collections.Generic.List<string>", "System_Collections_Generic_List_string_")]
+    public void ToBuiltInSuffix_ProducesValidIdentifier(string typeName, string expected)
+    {
+        var result = JsonContextGenerator.ToBuiltInSuffix(typeName);
+        Assert.Equal(expected, result);
+    }
+
+    [Fact]
+    public void ToBuiltInSuffix_NestedGenericType_SanitizesAngleBrackets()
+    {
+        var result = JsonContextGenerator.ToBuiltInSuffix("System.Collections.Generic.List<string>");
+
+        Assert.DoesNotContain("<", result);
+        Assert.DoesNotContain(">", result);
+        Assert.Equal("System_Collections_Generic_List_string_", result);
+    }
+}