diff --git a/src/NHibernate.Test/MappingByCode/IntegrationTests/NH3110/Fixture.cs b/src/NHibernate.Test/MappingByCode/IntegrationTests/NH3110/Fixture.cs
new file mode 100644
index 00000000000..4a1a1b405ce
--- /dev/null
+++ b/src/NHibernate.Test/MappingByCode/IntegrationTests/NH3110/Fixture.cs
@@ -0,0 +1,26 @@
+using System.Linq;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Mapping.ByCode;
+using NUnit.Framework;
+
+namespace NHibernate.Test.MappingByCode.IntegrationTests.NH3110
+{
+	[TestFixture]
+	public class Fixture
+	{
+		[Test]
+		public void CanSetPolymorphism()
+		{
+			var mapper = new ModelMapper();
+			mapper.Class<Entity>(rc =>
+			{
+				rc.Polymorphism(PolymorphismType.Explicit);
+			});
+
+			var mapping = mapper.CompileMappingForAllExplicitlyAddedEntities();
+
+			var entity = mapping.RootClasses[0];
+			Assert.AreEqual(entity.polymorphism, HbmPolymorphismType.Explicit);
+		}
+	}
+}
\ No newline at end of file
diff --git a/src/NHibernate.Test/NHibernate.Test.csproj b/src/NHibernate.Test/NHibernate.Test.csproj
index ad6d1b9ca10..069221382f3 100644
--- a/src/NHibernate.Test/NHibernate.Test.csproj
+++ b/src/NHibernate.Test/NHibernate.Test.csproj
@@ -605,6 +605,7 @@
     <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\NH3110\Fixture.cs" />
     <Compile Include="MappingByCode\IntegrationTests\NH3135\Fixture.cs" />
     <Compile Include="MappingByCode\IntegrationTests\NH3135\Models.cs" />
     <Compile Include="MappingByCode\IntegrationTests\NH3280\Domain.cs" />
diff --git a/src/NHibernate/Mapping/ByCode/IClassMapper.cs b/src/NHibernate/Mapping/ByCode/IClassMapper.cs
index 80304061f67..60defe318a6 100644
--- a/src/NHibernate/Mapping/ByCode/IClassMapper.cs
+++ b/src/NHibernate/Mapping/ByCode/IClassMapper.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Linq.Expressions;
 using System.Reflection;
+using NHibernate.Cfg.MappingSchema;
 
 namespace NHibernate.Mapping.ByCode
 {
@@ -25,6 +26,7 @@ public interface IClassAttributesMapper : IEntityAttributesMapper, IEntitySqlsMa
 		void Filter(string filterName, Action<IFilterMapper> filterMapping);
 		void Where(string whereClause);
 		void SchemaAction(SchemaAction action);
+		void Polymorphism(PolymorphismType type);
 	}
 
 	public interface IClassMapper : IClassAttributesMapper, IPropertyContainerMapper
@@ -64,6 +66,7 @@ public interface IClassAttributesMapper<TEntity> : IEntityAttributesMapper, IEnt
 		void Filter(string filterName, Action<IFilterMapper> filterMapping);
 		void Where(string whereClause);
 		void SchemaAction(SchemaAction action);
+		void Polymorphism(PolymorphismType type);
 	}
 
 	public interface IClassMapper<TEntity> : IClassAttributesMapper<TEntity>, IPropertyContainerMapper<TEntity> where TEntity : class
diff --git a/src/NHibernate/Mapping/ByCode/Impl/ClassMapper.cs b/src/NHibernate/Mapping/ByCode/Impl/ClassMapper.cs
index 6c1d4916031..dfd17f13a2d 100644
--- a/src/NHibernate/Mapping/ByCode/Impl/ClassMapper.cs
+++ b/src/NHibernate/Mapping/ByCode/Impl/ClassMapper.cs
@@ -256,6 +256,10 @@ public void Join(string splitGroupId, Action<IJoinMapper> splitMapping)
 			splitMapping(splitGroup);
 		}
 
+		public void Polymorphism(PolymorphismType type)
+		{
+			classMapping.polymorphism = (HbmPolymorphismType) Enum.Parse(typeof(HbmPolymorphismType), type.ToString());
+		}
 		#endregion
 
 		#region Implementation of IEntityAttributesMapper
diff --git a/src/NHibernate/Mapping/ByCode/Impl/CustomizersImpl/ClassCustomizer.cs b/src/NHibernate/Mapping/ByCode/Impl/CustomizersImpl/ClassCustomizer.cs
index 4b25dfd56e5..fdd2c330135 100644
--- a/src/NHibernate/Mapping/ByCode/Impl/CustomizersImpl/ClassCustomizer.cs
+++ b/src/NHibernate/Mapping/ByCode/Impl/CustomizersImpl/ClassCustomizer.cs
@@ -116,6 +116,11 @@ public void Schema(string schemaName)
 			CustomizersHolder.AddCustomizer(typeof(TEntity), (IClassMapper m) => m.Schema(schemaName));
 		}
 
+		public void Polymorphism(PolymorphismType type)
+		{
+			CustomizersHolder.AddCustomizer(typeof(TEntity), (IClassMapper m) => m.Polymorphism(type));
+		}
+
 		#endregion
 
 		#region Implementation of IEntityAttributesMapper
diff --git a/src/NHibernate/Mapping/ByCode/PolymorphismType.cs b/src/NHibernate/Mapping/ByCode/PolymorphismType.cs
new file mode 100644
index 00000000000..a1450974677
--- /dev/null
+++ b/src/NHibernate/Mapping/ByCode/PolymorphismType.cs
@@ -0,0 +1,23 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace NHibernate.Mapping.ByCode
+{
+	/// <summary>
+	/// The possible types of polymorphism for IClassMapper.
+	/// </summary>
+	public enum PolymorphismType
+	{
+		/// <summary>
+		/// Implicit polymorphism
+		/// </summary>
+		Implicit,
+
+		/// <summary>
+		/// Explicit polymorphism
+		/// </summary>
+		Explicit
+	}
+}
diff --git a/src/NHibernate/NHibernate.csproj b/src/NHibernate/NHibernate.csproj
index b399d058ce9..1cf454d984c 100644
--- a/src/NHibernate/NHibernate.csproj
+++ b/src/NHibernate/NHibernate.csproj
@@ -354,6 +354,7 @@
     <Compile Include="Mapping\ByCode\Impl\DynamicComponentMapper.cs" />
     <Compile Include="Mapping\ByCode\Impl\ManyToAnyMapper.cs" />
     <Compile Include="Mapping\ByCode\Import.cs" />
+    <Compile Include="Mapping\ByCode\PolymorphismType.cs" />
     <Compile Include="Mapping\ByCode\PropertyGeneration.cs" />
     <Compile Include="Mapping\ByCode\PropertyToField.cs" />
     <Compile Include="Mapping\ByCode\SimpleModelInspector.cs" />