diff --git a/src/FluentNHibernate.Testing/ConventionsTests/OverridingFluentInterface/PropertyConventionTests.cs b/src/FluentNHibernate.Testing/ConventionsTests/OverridingFluentInterface/PropertyConventionTests.cs
index 3a1ce8a36..651a08b9d 100644
--- a/src/FluentNHibernate.Testing/ConventionsTests/OverridingFluentInterface/PropertyConventionTests.cs
+++ b/src/FluentNHibernate.Testing/ConventionsTests/OverridingFluentInterface/PropertyConventionTests.cs
@@ -65,7 +65,7 @@ public void TypeShouldntBeOverwritten()
 
         Convention(x => x.CustomType<int>());
 
-        VerifyModel(x => x.Type.Name.ShouldEqual(typeof(CustomUserType).AssemblyQualifiedName));
+        VerifyModel(x => x.Type.GetUnderlyingSystemType().ShouldEqual(typeof(CustomUserType)));
     }
 
     [Test]
@@ -285,4 +285,4 @@ void VerifyModel(Action<PropertyMapping> modelVerification)
     }
 
     #endregion
-}
+}
\ No newline at end of file
diff --git a/src/FluentNHibernate.Testing/DomainModel/Mapping/ClassMapConventionsTester.cs b/src/FluentNHibernate.Testing/DomainModel/Mapping/ClassMapConventionsTester.cs
index 764f2939e..d0a83efa4 100644
--- a/src/FluentNHibernate.Testing/DomainModel/Mapping/ClassMapConventionsTester.cs
+++ b/src/FluentNHibernate.Testing/DomainModel/Mapping/ClassMapConventionsTester.cs
@@ -108,6 +108,6 @@ public void EnumsDontGetTypeOverriddenByConventionsIfExplicitlySet()
     {
         new MappingTester<MappedObject>()
             .ForMapping(m => m.Map(x => x.Color).CustomType(typeof(int)))
-            .Element("class/property[@name='Color']").HasAttribute("type", typeof(int).Name);
+            .Element("class/property[@name='Color']").HasAttribute("type", typeof(int).AssemblyQualifiedName);
     }
-}
+}
\ No newline at end of file
diff --git a/src/FluentNHibernate/Mapping/PropertyPart.cs b/src/FluentNHibernate/Mapping/PropertyPart.cs
index 03245b20f..740c25030 100644
--- a/src/FluentNHibernate/Mapping/PropertyPart.cs
+++ b/src/FluentNHibernate/Mapping/PropertyPart.cs
@@ -12,8 +12,8 @@ public class PropertyPart : IPropertyMappingProvider
 {
     readonly Member member;
     readonly Type parentType;
-    readonly AttributeStore attributes = new AttributeStore();
-    readonly AttributeStore columnAttributes = new AttributeStore();
+    readonly AttributeStore attributes = new();
+    readonly AttributeStore columnAttributes = new();
 
     bool nextBool = true;
 
@@ -171,7 +171,8 @@ public PropertyPart CustomType(Type type)
         if (typeof(ICompositeUserType).IsAssignableFrom(type))
             AddColumnsFromCompositeUserType(type);
 
-        return CustomType(TypeMapping.GetTypeString(type));
+        attributes.Set("Type", Layer.UserSupplied, new TypeReference(type));
+        return this;
     }
 
     /// <summary>
@@ -194,11 +195,7 @@ public PropertyPart CustomType(string type)
     public PropertyPart CustomType(Func<Type, Type> typeFunc)
     {
         var type = typeFunc.Invoke(member.PropertyType);
-
-        if (typeof(ICompositeUserType).IsAssignableFrom(type))
-            AddColumnsFromCompositeUserType(type);
-
-        return CustomType(TypeMapping.GetTypeString(type));
+        return CustomType(type);
     }
 
     void AddColumnsFromCompositeUserType(Type compositeUserType)