diff --git a/src/NHibernate.Test/MappingByCode/IntegrationTests/NH3527/FixtureByCode.cs b/src/NHibernate.Test/MappingByCode/IntegrationTests/NH3527/FixtureByCode.cs
new file mode 100644
index 00000000000..6f32fb85cdb
--- /dev/null
+++ b/src/NHibernate.Test/MappingByCode/IntegrationTests/NH3527/FixtureByCode.cs
@@ -0,0 +1,72 @@
+using System;
+using System.Collections.Generic;
+using System.Data;
+using System.Data.Common;
+using System.Linq;
+using System.Text;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Dialect;
+using NHibernate.Mapping.ByCode;
+using NUnit.Framework;
+using SharpTestsEx;
+
+namespace NHibernate.Test.MappingByCode.IntegrationTests.NH3527
+{
+	[TestFixture]
+	public class FixtureByCode : TestCaseMappingByCode
+	{
+		[Test]
+		public void VerifyMapping()
+		{
+			var mapping = this.GetMappings();
+
+			// Item mapping.
+			mapping.UnionSubclasses[0].abstractSpecified.Should().Be.True();
+			mapping.UnionSubclasses[0].@abstract.Should().Be.True();
+			// InventoryItem mapping.
+			mapping.UnionSubclasses[1].abstractSpecified.Should().Be.False();
+			mapping.UnionSubclasses[1].@abstract.Should().Be.False();
+		}
+
+		[Test]
+		public void VerifyTables()
+		{
+			using (var session = this.OpenSession())
+			{
+				var tableNameColumnName = "TABLE_NAME";
+				var itemTableName = "Item";
+				var inventoryItemTableName = "InventoryItem";
+
+				var schema = this.Dialect.GetDataBaseSchema((DbConnection) session.Connection);
+				var tables = schema.GetTables(null, null, null, null).AsEnumerable();
+				var itemTable = tables.SingleOrDefault(
+					x => string.Equals(x.Field<string>(tableNameColumnName),
+					                   itemTableName,
+					                   StringComparison.InvariantCultureIgnoreCase));
+				var inventoryItemTable = tables.SingleOrDefault(
+					x => string.Equals(x.Field<string>(tableNameColumnName),
+					                   inventoryItemTableName,
+					                   StringComparison.InvariantCultureIgnoreCase));
+
+				itemTable.Should().Be.Null();
+				inventoryItemTable.Should().Not.Be.Null();
+			}
+		}
+
+		protected override bool AppliesTo(Dialect.Dialect dialect)
+		{
+			return dialect is MsSql2008Dialect;
+		}
+
+		protected override HbmMapping GetMappings()
+		{
+			var mapper = new ModelMapper();
+			mapper.Class<EntityBase>(
+				m => m.Id(x => x.Id, im => im.Generator(Generators.HighLow)));
+			mapper.UnionSubclass<Item>(m => { });
+			mapper.UnionSubclass<InventoryItem>(m => { });
+
+			return mapper.CompileMappingForAllExplicitlyAddedEntities();
+		}
+	}
+}
diff --git a/src/NHibernate.Test/MappingByCode/IntegrationTests/NH3527/Model.cs b/src/NHibernate.Test/MappingByCode/IntegrationTests/NH3527/Model.cs
new file mode 100644
index 00000000000..63ef75cc75e
--- /dev/null
+++ b/src/NHibernate.Test/MappingByCode/IntegrationTests/NH3527/Model.cs
@@ -0,0 +1,20 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace NHibernate.Test.MappingByCode.IntegrationTests.NH3527
+{
+	public abstract class EntityBase
+	{
+		public virtual int Id { get; set; }
+	}
+
+	public abstract class Item : EntityBase
+	{
+	}
+
+	public class InventoryItem : Item
+	{
+	}
+}
diff --git a/src/NHibernate.Test/MappingByCode/MappersTests/UnionSubclassMapperTests/AbstractAttributeTests.cs b/src/NHibernate.Test/MappingByCode/MappersTests/UnionSubclassMapperTests/AbstractAttributeTests.cs
new file mode 100644
index 00000000000..9a128e5fb31
--- /dev/null
+++ b/src/NHibernate.Test/MappingByCode/MappersTests/UnionSubclassMapperTests/AbstractAttributeTests.cs
@@ -0,0 +1,47 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Mapping.ByCode.Impl;
+using NUnit.Framework;
+using SharpTestsEx;
+
+namespace NHibernate.Test.MappingByCode.MappersTests.UnionSubclassMapperTests
+{
+	[TestFixture]
+	public class AbstractAttributeTests
+	{
+		private abstract class EntityBase
+		{
+		}
+
+		private abstract class Item : EntityBase
+		{
+		}
+
+		private class InventoryItem : Item
+		{
+		}
+
+		[Test]
+		public void CanSetAbstractAttributeOnAbstractClass()
+		{
+			var mapping = new HbmMapping();
+			var mapper = new UnionSubclassMapper(typeof(Item), mapping);
+
+			mapping.UnionSubclasses[0].abstractSpecified.Should().Be.True();
+			mapping.UnionSubclasses[0].@abstract.Should().Be.True();
+		}
+
+		[Test]
+		public void CanSetAbstractAttributeOnConcreteClass()
+		{
+			var mapping = new HbmMapping();
+			var mapper = new UnionSubclassMapper(typeof(InventoryItem), mapping);
+
+			mapping.UnionSubclasses[0].abstractSpecified.Should().Be.False();
+			mapping.UnionSubclasses[0].@abstract.Should().Be.False();
+		}
+	}
+}
diff --git a/src/NHibernate.Test/NHibernate.Test.csproj b/src/NHibernate.Test/NHibernate.Test.csproj
index e9367d71425..3398e821ec4 100644
--- a/src/NHibernate.Test/NHibernate.Test.csproj
+++ b/src/NHibernate.Test/NHibernate.Test.csproj
@@ -90,6 +90,7 @@
       <RequiredTargetFramework>3.5</RequiredTargetFramework>
     </Reference>
     <Reference Include="System.Data" />
+    <Reference Include="System.Data.DataSetExtensions" />
     <Reference Include="System.Data.OracleClient" />
     <Reference Include="System.Drawing" />
     <Reference Include="System.Linq.Dynamic, Version=1.0.0.0, Culture=neutral, processorArchitecture=MSIL">
@@ -589,6 +590,10 @@
     <Compile Include="MappingByCode\IntegrationTests\NH2825\Fixture.cs" />
     <Compile Include="MappingByCode\IntegrationTests\NH2825\FixtureByCode.cs" />
     <Compile Include="MappingByCode\IntegrationTests\NH2825\Parent.cs" />
+    <Compile Include="MappingByCode\IntegrationTests\NH3280\Domain.cs" />
+    <Compile Include="MappingByCode\IntegrationTests\NH3280\OneToOneToInheritedProperty.cs" />
+    <Compile Include="MappingByCode\IntegrationTests\NH3527\Model.cs" />
+    <Compile Include="MappingByCode\IntegrationTests\NH3527\FixtureByCode.cs" />
     <Compile Include="MappingByCode\MappersTests\AnyMapperTest.cs" />
     <Compile Include="MappingByCode\MappersTests\IdMapperTest.cs" />
     <Compile Include="MappingByCode\MappersTests\ManyToOneMapperTest.cs" />
@@ -625,6 +630,7 @@
     <Compile Include="MappingByCode\MappersTests\SubclassMapperTests\SetPersisterTests.cs" />
     <Compile Include="MappingByCode\MappersTests\SubclassMapperTests\TablesSincronizationTests.cs" />
     <Compile Include="MappingByCode\MappersTests\SubclassMapperWithJoinPropertiesTest.cs" />
+    <Compile Include="MappingByCode\MappersTests\UnionSubclassMapperTests\AbstractAttributeTests.cs" />
     <Compile Include="MappingByCode\MappersTests\UnionSubclassMapperTests\SetPersisterTests.cs" />
     <Compile Include="MappingByCode\MappersTests\UnionSubclassMapperTests\TablesSincronizationTests.cs" />
     <Compile Include="MappingByCode\MixAutomapping\ArrayCollectionTests.cs" />
diff --git a/src/NHibernate/Mapping/ByCode/Impl/UnionSubclassMapper.cs b/src/NHibernate/Mapping/ByCode/Impl/UnionSubclassMapper.cs
index 2ad3b266d29..630acaa5691 100644
--- a/src/NHibernate/Mapping/ByCode/Impl/UnionSubclassMapper.cs
+++ b/src/NHibernate/Mapping/ByCode/Impl/UnionSubclassMapper.cs
@@ -17,6 +17,11 @@ public UnionSubclassMapper(System.Type subClass, HbmMapping mapDoc)
 			var toAdd = new[] {classMapping};
 			classMapping.name = subClass.GetShortClassName(mapDoc);
 			classMapping.extends = subClass.BaseType.GetShortClassName(mapDoc);
+			if (subClass.IsAbstract)
+			{
+				classMapping.@abstract = true;
+				classMapping.abstractSpecified = true;
+			}
 			mapDoc.Items = mapDoc.Items == null ? toAdd : mapDoc.Items.Concat(toAdd).ToArray();
 		}