diff --git a/src/NHibernate.Test/Async/NHSpecificTest/GH3289/FixtureByCode.cs b/src/NHibernate.Test/Async/NHSpecificTest/GH3289/FixtureByCode.cs
new file mode 100644
index 00000000000..721d35848ab
--- /dev/null
+++ b/src/NHibernate.Test/Async/NHSpecificTest/GH3289/FixtureByCode.cs
@@ -0,0 +1,111 @@
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by AsyncGenerator.
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+
+
+using System.Linq;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Linq;
+using NHibernate.Mapping.ByCode;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH3289
+{
+	using System.Threading.Tasks;
+	[TestFixture]
+	public class ByCodeFixtureAsync : TestCaseMappingByCode
+	{
+		protected override HbmMapping GetMappings()
+		{
+			var mapper = new ModelMapper();
+			mapper.Class<Entity>(rc =>
+			{
+				rc.Id(x => x.Id, m => m.Generator(Generators.Identity));
+				rc.Property(x => x.Name);
+				rc.Component(x => x.Component);
+			});
+			mapper.Class<OtherEntity>(rc =>
+			{
+				rc.Id(x => x.Id, m => m.Generator(Generators.Identity));
+				rc.Property(x => x.Name);
+				rc.Component(x => x.Component);
+			});
+			mapper.JoinedSubclass<SubEntity>(rc =>
+			{
+				rc.Key(k => k.Column("Id"));
+				rc.Property(x => x.SomeProperty);
+			});
+			mapper.Component<Component>(rc =>
+			{
+				rc.Property(x => x.Field);
+				rc.Lazy(true);
+			});
+
+			return mapper.CompileMappingForAllExplicitlyAddedEntities();
+		}
+
+		protected override void OnSetUp()
+		{
+			using var session = OpenSession();
+			using var transaction = session.BeginTransaction();
+			var e1 = new SubEntity { Name = "Jim" };
+			session.Save(e1);
+
+			transaction.Commit();
+		}
+
+		protected override void OnTearDown()
+		{
+			using var session = OpenSession();
+			using var transaction = session.BeginTransaction();
+
+			if (Dialect.SupportsTemporaryTables)
+				session.CreateQuery("delete from System.Object").ExecuteUpdate();
+			else
+				session.Delete("from System.Object");
+
+			transaction.Commit();
+		}
+
+		[Test]
+		public async Task TestSubEntityInterfaceWithFetchIsPropertyInitializedAsync()
+		{
+			using var session = OpenSession();
+			var data = await (session.Query<ISubEntity>()
+				.Fetch(e => e.Component)
+				.ToListAsync());
+			var result = NHibernateUtil.IsPropertyInitialized(data[0], "Component");
+
+			Assert.That(result, Is.True);
+		}
+
+		[Test]
+		public async Task TestEntityInterfaceWithFetchIsPropertyInitializedAsync()
+		{
+			using var session = OpenSession();
+			var data = await (session.Query<IEntity>()
+				.Fetch(e => e.Component)
+				.ToListAsync());
+			var result = NHibernateUtil.IsPropertyInitialized(data[0], "Component");
+
+			Assert.That(result, Is.True);
+		}
+
+		[Test]
+		public async Task TestSubEntityWithFetchIsPropertyInitializedAsync()
+		{
+			using var session = OpenSession();
+			var data = await (session.Query<SubEntity>()
+				.Fetch(e => e.Component)
+				.ToListAsync());
+			var result = NHibernateUtil.IsPropertyInitialized(data[0], "Component");
+
+			Assert.That(result, Is.True);
+		}
+	}
+}
diff --git a/src/NHibernate.Test/NHSpecificTest/GH3289/FixtureByCode.cs b/src/NHibernate.Test/NHSpecificTest/GH3289/FixtureByCode.cs
new file mode 100644
index 00000000000..8bc20205c12
--- /dev/null
+++ b/src/NHibernate.Test/NHSpecificTest/GH3289/FixtureByCode.cs
@@ -0,0 +1,100 @@
+using System.Linq;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Linq;
+using NHibernate.Mapping.ByCode;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH3289
+{
+	[TestFixture]
+	public class ByCodeFixture : TestCaseMappingByCode
+	{
+		protected override HbmMapping GetMappings()
+		{
+			var mapper = new ModelMapper();
+			mapper.Class<Entity>(rc =>
+			{
+				rc.Id(x => x.Id, m => m.Generator(Generators.Identity));
+				rc.Property(x => x.Name);
+				rc.Component(x => x.Component);
+			});
+			mapper.Class<OtherEntity>(rc =>
+			{
+				rc.Id(x => x.Id, m => m.Generator(Generators.Identity));
+				rc.Property(x => x.Name);
+				rc.Component(x => x.Component);
+			});
+			mapper.JoinedSubclass<SubEntity>(rc =>
+			{
+				rc.Key(k => k.Column("Id"));
+				rc.Property(x => x.SomeProperty);
+			});
+			mapper.Component<Component>(rc =>
+			{
+				rc.Property(x => x.Field);
+				rc.Lazy(true);
+			});
+
+			return mapper.CompileMappingForAllExplicitlyAddedEntities();
+		}
+
+		protected override void OnSetUp()
+		{
+			using var session = OpenSession();
+			using var transaction = session.BeginTransaction();
+			var e1 = new SubEntity { Name = "Jim" };
+			session.Save(e1);
+
+			transaction.Commit();
+		}
+
+		protected override void OnTearDown()
+		{
+			using var session = OpenSession();
+			using var transaction = session.BeginTransaction();
+
+			if (Dialect.SupportsTemporaryTables)
+				session.CreateQuery("delete from System.Object").ExecuteUpdate();
+			else
+				session.Delete("from System.Object");
+
+			transaction.Commit();
+		}
+
+		[Test]
+		public void TestSubEntityInterfaceWithFetchIsPropertyInitialized()
+		{
+			using var session = OpenSession();
+			var data = session.Query<ISubEntity>()
+				.Fetch(e => e.Component)
+				.ToList();
+			var result = NHibernateUtil.IsPropertyInitialized(data[0], "Component");
+
+			Assert.That(result, Is.True);
+		}
+
+		[Test]
+		public void TestEntityInterfaceWithFetchIsPropertyInitialized()
+		{
+			using var session = OpenSession();
+			var data = session.Query<IEntity>()
+				.Fetch(e => e.Component)
+				.ToList();
+			var result = NHibernateUtil.IsPropertyInitialized(data[0], "Component");
+
+			Assert.That(result, Is.True);
+		}
+
+		[Test]
+		public void TestSubEntityWithFetchIsPropertyInitialized()
+		{
+			using var session = OpenSession();
+			var data = session.Query<SubEntity>()
+				.Fetch(e => e.Component)
+				.ToList();
+			var result = NHibernateUtil.IsPropertyInitialized(data[0], "Component");
+
+			Assert.That(result, Is.True);
+		}
+	}
+}
diff --git a/src/NHibernate.Test/NHSpecificTest/GH3289/Models.cs b/src/NHibernate.Test/NHSpecificTest/GH3289/Models.cs
new file mode 100644
index 00000000000..ffbbeeb7bf7
--- /dev/null
+++ b/src/NHibernate.Test/NHSpecificTest/GH3289/Models.cs
@@ -0,0 +1,37 @@
+namespace NHibernate.Test.NHSpecificTest.GH3289
+{
+	public interface IEntity
+	{
+		int Id { get; set; }
+		string Name { get; set; }
+		Component Component { get; set; }
+	}
+
+	public interface ISubEntity : IEntity
+	{
+		public bool SomeProperty { get; set; }
+	}
+
+	public class Entity : IEntity
+	{
+		public virtual int Id { get; set; }
+		public virtual string Name { get; set; }
+		public virtual Component Component { get; set; }
+	}
+	public class OtherEntity : IEntity
+	{
+		public virtual int Id { get; set; }
+		public virtual string Name { get; set; }
+		public virtual Component Component { get; set; }
+	}
+
+	public class SubEntity : Entity, ISubEntity
+	{
+		public virtual bool SomeProperty { get; set; }
+	}
+
+	public class Component
+	{
+		public virtual string Field { get; set; }
+	}
+}
diff --git a/src/NHibernate/Linq/Visitors/ResultOperatorProcessors/ProcessFetch.cs b/src/NHibernate/Linq/Visitors/ResultOperatorProcessors/ProcessFetch.cs
index a042af3c12d..31401f7df81 100644
--- a/src/NHibernate/Linq/Visitors/ResultOperatorProcessors/ProcessFetch.cs
+++ b/src/NHibernate/Linq/Visitors/ResultOperatorProcessors/ProcessFetch.cs
@@ -52,6 +52,16 @@ private void Process(
 				{
 					var metadata = queryModelVisitor.VisitorParameters.SessionFactory
 													.GetClassMetadata(resultOperator.RelationMember.ReflectedType);
+					if (metadata == null)
+					{
+						var entityName = queryModelVisitor.VisitorParameters.SessionFactory.GetImplementors(
+							resultOperator.RelationMember.ReflectedType.FullName).FirstOrDefault();
+						if (!string.IsNullOrEmpty(entityName))
+						{
+							metadata = queryModelVisitor.VisitorParameters.SessionFactory.GetClassMetadata(entityName);
+						}
+					}
+
 					propType = metadata?.GetPropertyType(resultOperator.RelationMember.Name);
 				}