diff --git a/src/NHibernate.Test/MappingByCode/ExplicitMappingTests/OptimisticLockModeTests.cs b/src/NHibernate.Test/MappingByCode/ExplicitMappingTests/OptimisticLockModeTests.cs
new file mode 100644
index 00000000000..5d18dccfa59
--- /dev/null
+++ b/src/NHibernate.Test/MappingByCode/ExplicitMappingTests/OptimisticLockModeTests.cs
@@ -0,0 +1,33 @@
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Mapping.ByCode;
+using NUnit.Framework;
+using SharpTestsEx;
+
+namespace NHibernate.Test.MappingByCode.ExplicitMappingTests
+{
+	[TestFixture]
+	public class OptimisticLockModeTests
+	{
+		private class MyClass
+		{
+			public int Id { get; set; }
+			public int Version { get; set; }
+		}
+
+		[Test]
+		public void OptimisticLockModeTest()
+		{
+			//NH-2823
+			var mapper = new ModelMapper();
+			mapper.Class<MyClass>(
+				map =>
+				{
+					map.Id(x => x.Id, idmap => { });
+					map.OptimisticLock(OptimisticLockMode.Dirty);
+				});
+
+			var mappings = mapper.CompileMappingForAllExplicitlyAddedEntities();
+			Assert.AreEqual(mappings.RootClasses[0].optimisticlock, HbmOptimisticLockMode.Dirty);
+		}
+	}
+}
\ No newline at end of file
diff --git a/src/NHibernate.Test/NHibernate.Test.csproj b/src/NHibernate.Test/NHibernate.Test.csproj
index 069221382f3..f6eee9f1b07 100644
--- a/src/NHibernate.Test/NHibernate.Test.csproj
+++ b/src/NHibernate.Test/NHibernate.Test.csproj
@@ -588,6 +588,7 @@
     <Compile Include="MappingByCode\ExplicitMappingTests\PoidTests.cs" />
     <Compile Include="MappingByCode\ExplicitMappingTests\RootClassPropertiesSplitsTests.cs" />
     <Compile Include="MappingByCode\ExplicitMappingTests\SubclassPropertiesSplitsTests.cs" />
+    <Compile Include="MappingByCode\ExplicitMappingTests\OptimisticLockModeTests.cs" />
     <Compile Include="MappingByCode\ExplicitMappingTests\VersionTests.cs" />
     <Compile Include="MappingByCode\For.cs" />
     <Compile Include="MappingByCode\GeneratorTests.cs" />
diff --git a/src/NHibernate/Mapping/ByCode/IClassMapper.cs b/src/NHibernate/Mapping/ByCode/IClassMapper.cs
index 60defe318a6..b472db56cc2 100644
--- a/src/NHibernate/Mapping/ByCode/IClassMapper.cs
+++ b/src/NHibernate/Mapping/ByCode/IClassMapper.cs
@@ -27,6 +27,7 @@ public interface IClassAttributesMapper : IEntityAttributesMapper, IEntitySqlsMa
 		void Where(string whereClause);
 		void SchemaAction(SchemaAction action);
 		void Polymorphism(PolymorphismType type);
+		void OptimisticLock(OptimisticLockMode mode);
 	}
 
 	public interface IClassMapper : IClassAttributesMapper, IPropertyContainerMapper
@@ -67,6 +68,7 @@ public interface IClassAttributesMapper<TEntity> : IEntityAttributesMapper, IEnt
 		void Where(string whereClause);
 		void SchemaAction(SchemaAction action);
 		void Polymorphism(PolymorphismType type);
+		void OptimisticLock(OptimisticLockMode mode);
 	}
 
 	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 dfd17f13a2d..2bfc5cdf439 100644
--- a/src/NHibernate/Mapping/ByCode/Impl/ClassMapper.cs
+++ b/src/NHibernate/Mapping/ByCode/Impl/ClassMapper.cs
@@ -59,6 +59,10 @@ public Dictionary<string, IJoinMapper> JoinMappers
 		}
 
 		#region Implementation of IClassMapper
+		public void OptimisticLock(OptimisticLockMode mode)
+		{
+			classMapping.optimisticlock = (HbmOptimisticLockMode)Enum.Parse(typeof(OptimisticLockMode), mode.ToString());
+		}
 
 		public void Id(Action<IIdMapper> mapper)
 		{
diff --git a/src/NHibernate/Mapping/ByCode/Impl/CustomizersImpl/ClassCustomizer.cs b/src/NHibernate/Mapping/ByCode/Impl/CustomizersImpl/ClassCustomizer.cs
index fdd2c330135..4c398928811 100644
--- a/src/NHibernate/Mapping/ByCode/Impl/CustomizersImpl/ClassCustomizer.cs
+++ b/src/NHibernate/Mapping/ByCode/Impl/CustomizersImpl/ClassCustomizer.cs
@@ -30,6 +30,11 @@ private Dictionary<string, IJoinMapper<TEntity>> JoinCustomizers
 
 		#region Implementation of IClassAttributesMapper<TEntity>
 
+		public void OptimisticLock(OptimisticLockMode mode)
+		{
+			CustomizersHolder.AddCustomizer(typeof(TEntity), (IClassMapper m) => m.OptimisticLock(mode));
+		}
+
 		public void Id<TProperty>(Expression<Func<TEntity, TProperty>> idProperty)
 		{
 			Id(idProperty, x => { });
diff --git a/src/NHibernate/Mapping/ByCode/OptimisticLockMode.cs b/src/NHibernate/Mapping/ByCode/OptimisticLockMode.cs
new file mode 100644
index 00000000000..58e41f30d7e
--- /dev/null
+++ b/src/NHibernate/Mapping/ByCode/OptimisticLockMode.cs
@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace NHibernate.Mapping.ByCode
+{
+	public enum OptimisticLockMode
+	{
+		None,
+
+		Version,
+
+		Dirty,
+
+		All,
+	}
+}
diff --git a/src/NHibernate/NHibernate.csproj b/src/NHibernate/NHibernate.csproj
index 1cf454d984c..54fa348f4e2 100644
--- a/src/NHibernate/NHibernate.csproj
+++ b/src/NHibernate/NHibernate.csproj
@@ -353,6 +353,7 @@
     <Compile Include="Mapping\ByCode\Impl\CustomizersImpl\ManyToAnyCustomizer.cs" />
     <Compile Include="Mapping\ByCode\Impl\DynamicComponentMapper.cs" />
     <Compile Include="Mapping\ByCode\Impl\ManyToAnyMapper.cs" />
+    <Compile Include="Mapping\ByCode\OptimisticLockMode.cs" />
     <Compile Include="Mapping\ByCode\Import.cs" />
     <Compile Include="Mapping\ByCode\PolymorphismType.cs" />
     <Compile Include="Mapping\ByCode\PropertyGeneration.cs" />