diff --git a/src/FluentNHibernate.Testing/Cfg/DuplicateMappingTests.cs b/src/FluentNHibernate.Testing/Cfg/DuplicateMappingTests.cs
new file mode 100644
index 000000000..8c36a3477
--- /dev/null
+++ b/src/FluentNHibernate.Testing/Cfg/DuplicateMappingTests.cs
@@ -0,0 +1,80 @@
+using FluentNHibernate.Automapping;
+using FluentNHibernate.Cfg;
+using FluentNHibernate.Cfg.Db;
+using FluentNHibernate.Mapping;
+using NHibernate.Cfg;
+using NHibernate.Mapping;
+using NUnit.Framework;
+
+namespace FluentNHibernate.Testing.Cfg
+{
+    [TestFixture]
+    public class DuplicateMappingTests
+    {
+        private Configuration cfg;
+        private MappingConfiguration mapping;
+
+        [SetUp]
+        public void CreateMappingConfiguration()
+        {
+            cfg = new Configuration();
+
+            SQLiteConfiguration.Standard
+                .InMemory()
+                .ConfigureProperties(cfg);
+
+            mapping = new MappingConfiguration();
+        }
+
+        [Test]
+        public void FluentMappingOfInheritedAutomappedTypeShouldBeIgnoredForSubclasses()
+        {
+            mapping.FluentMappings.Add(typeof(TypeInfoMap));
+            mapping.FluentMappings.Add(typeof(MessageTypeMap));
+            mapping.AutoMappings.Add(AutoMap.Source(new StubTypeSource(typeof(ActiveRecord))));
+            mapping.Apply(cfg);
+
+            var arMapping = cfg.GetClassMapping(typeof(ActiveRecord));
+            arMapping.SubclassIterator.GetEnumerator().MoveNext().ShouldBeFalse();
+            var messageTypeMapping = cfg.GetClassMapping(typeof(MessageType)) as SingleTableSubclass;
+            messageTypeMapping.IsJoinedSubclass.ShouldBeFalse();
+        }
+
+        #region TestModel
+
+        public class ActiveRecord
+        {
+            public virtual int Id { get; set; }
+        }
+
+        public class TypeInfo : ActiveRecord
+        {
+            public virtual int ClassId { get; set; }
+        }
+
+        public class MessageType : TypeInfo
+        {
+        }
+
+        public class TypeInfoMap : ClassMap<TypeInfo>
+        {
+            public TypeInfoMap()
+            {
+                Table("TypeInfoNH");
+                Id(t => t.Id).GeneratedBy.HiLo("10");
+                Map(t => t.ClassId).ReadOnly();
+                DiscriminateSubClassesOnColumn("ClassId", 102);
+            }
+        }
+
+        public class MessageTypeMap : SubclassMap<MessageType>
+        {
+            public MessageTypeMap()
+            {
+                DiscriminatorValue(305);
+            }
+        }
+
+        #endregion
+    }
+}
diff --git a/src/FluentNHibernate.Testing/FluentNHibernate.Testing.csproj b/src/FluentNHibernate.Testing/FluentNHibernate.Testing.csproj
index 501dc5a9e..3a9970da6 100644
--- a/src/FluentNHibernate.Testing/FluentNHibernate.Testing.csproj
+++ b/src/FluentNHibernate.Testing/FluentNHibernate.Testing.csproj
@@ -126,6 +126,7 @@
     <Compile Include="AutoMapping\Overrides\CompositeIdOverrides.cs" />
     <Compile Include="AutoMapping\Overrides\HibernateMappingOverrides.cs" />
     <Compile Include="Cfg\Db\SqlAnywhereConfigurationTester.cs" />
+    <Compile Include="Cfg\DuplicateMappingTests.cs" />
     <Compile Include="DomainModel\Mapping\ManyToManySelfReferencedInverseIntegrationTester.cs" />
     <Compile Include="DomainModel\Mapping\MultipleKeyColumnsTester.cs" />
     <Compile Include="DomainModel\MemberAccessResolverTests.cs" />
@@ -416,10 +417,8 @@
     <Compile Include="Testing\Values\ReferencePropertySpecs.cs" />
     <Compile Include="Testing\Values\PropertySpecs.cs" />
     <Compile Include="Testing\Values\Entities.cs" />
-
     <Compile Include="Utils\ReflectionHelperTests.cs" />
     <Compile Include="Testing\XmlWriterTestHelper.cs" />
-
     <Compile Include="Utils\TypeReferenceEqualityTests.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Visitors\ComponentColumnPrefixVisitorSpecs.cs" />
diff --git a/src/FluentNHibernate/PersistenceModel.cs b/src/FluentNHibernate/PersistenceModel.cs
index 675256432..f81be8393 100644
--- a/src/FluentNHibernate/PersistenceModel.cs
+++ b/src/FluentNHibernate/PersistenceModel.cs
@@ -312,6 +312,8 @@ public bool ValidationEnabled
 
         internal void ImportProviders(PersistenceModel model)
         {
+            EnsureMappingsBuilt();
+
             model.classProviders.Each(x =>
             {
                 if (!classProviders.Contains(x))