diff --git a/src/NHibernate.Test/Async/NHSpecificTest/GH3134/ManyToManyChildFetchByCodeFixture.cs b/src/NHibernate.Test/Async/NHSpecificTest/GH3134/ManyToManyChildFetchByCodeFixture.cs
new file mode 100644
index 00000000000..0a5b10467f9
--- /dev/null
+++ b/src/NHibernate.Test/Async/NHSpecificTest/GH3134/ManyToManyChildFetchByCodeFixture.cs
@@ -0,0 +1,90 @@
+//------------------------------------------------------------------------------
+// <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.Collections.Generic;
+using System.Linq;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Mapping.ByCode;
+using NHibernate.Transform;
+using NHibernate.Util;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH3134
+{
+	using System.Threading.Tasks;
+	[TestFixture]
+	public class ManyToManyChildFetchByCodeFixtureAsync : TestCaseMappingByCode
+	{
+		protected override HbmMapping GetMappings()
+		{
+			var mapper = new ModelMapper();
+			mapper.AddMapping<AMap>();
+			mapper.AddMapping<BMap>();
+
+			return mapper.CompileMappingForAllExplicitlyAddedEntities();
+		}
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var a1 = new A();
+				a1.Bs.Add(new B());
+				a1.Bs.Add(new B());
+				session.Save(a1);
+
+				var a2 = new A();
+				a2.Bs.Add(new B());
+				a2.Bs.Add(new B());
+				session.Save(a2);
+
+				transaction.Commit();
+			}
+		}
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.Delete("from System.Object");
+
+				transaction.Commit();
+			}
+		}
+
+		[Test]
+		public async Task ChildFetchQueryOverAsync()
+		{
+			using (var session = OpenSession())
+			{
+				session.QueryOver<B>().Future();
+
+				session.QueryOver<B>()
+					.Fetch(SelectMode.ChildFetch, b => b)
+					.Fetch(SelectMode.Fetch, b => b.As)
+					.Future();
+
+				var result = (await (session.QueryOver<B>()
+					.Fetch(SelectMode.ChildFetch, b => b, b => b.As)
+					.Fetch(SelectMode.Fetch, b => b.As.First().Bs)
+					.TransformUsing(Transformers.DistinctRootEntity)
+					.Future()
+					.GetEnumerableAsync()))
+					.ToList();
+
+				Assert.That(result.Count, Is.EqualTo(4));
+				Assert.That(NHibernateUtil.IsInitialized(result[0].As), Is.True);
+				Assert.That(NHibernateUtil.IsInitialized(result[0].As.First().Bs), Is.True);
+				Assert.That(result[0].As.Count, Is.EqualTo(1));
+				Assert.That(result[0].As.First().Bs.Count, Is.EqualTo(2));
+			}
+		}
+	}
+}
diff --git a/src/NHibernate.Test/NHSpecificTest/GH3134/A.cs b/src/NHibernate.Test/NHSpecificTest/GH3134/A.cs
new file mode 100644
index 00000000000..fab1a02c8ff
--- /dev/null
+++ b/src/NHibernate.Test/NHSpecificTest/GH3134/A.cs
@@ -0,0 +1,12 @@
+using System;
+using System.Collections.Generic;
+
+namespace NHibernate.Test.NHSpecificTest.GH3134
+{
+	public class A
+	{
+		public virtual Guid Id { get; set; }
+		public virtual string NameA { get; set; }
+		public virtual ISet<B> Bs { get; set; } = new HashSet<B>();
+	}
+}
diff --git a/src/NHibernate.Test/NHSpecificTest/GH3134/AMap.cs b/src/NHibernate.Test/NHSpecificTest/GH3134/AMap.cs
new file mode 100644
index 00000000000..5e02c36a746
--- /dev/null
+++ b/src/NHibernate.Test/NHSpecificTest/GH3134/AMap.cs
@@ -0,0 +1,24 @@
+using NHibernate.Mapping.ByCode;
+using NHibernate.Mapping.ByCode.Conformist;
+
+namespace NHibernate.Test.NHSpecificTest.GH3134
+{
+	public class AMap : ClassMapping<A>
+	{
+		public AMap()
+		{
+			this.Table("A");
+			this.Id(x => x.Id, mapper => { mapper.Column("IDA"); mapper.Generator(Generators.Guid); });
+			Property(x => x.NameA);
+			this.Set(
+				x => x.Bs,
+				collectionMapping =>
+				{
+					collectionMapping.Table("AB");
+					collectionMapping.Key(k => { k.Column("A"); k.ForeignKey("none");});
+					collectionMapping.Cascade(Mapping.ByCode.Cascade.All);
+				},
+				map => map.ManyToMany(m => { m.Column("B"); }));
+		}
+	}
+}
diff --git a/src/NHibernate.Test/NHSpecificTest/GH3134/B.cs b/src/NHibernate.Test/NHSpecificTest/GH3134/B.cs
new file mode 100644
index 00000000000..c06b30226e8
--- /dev/null
+++ b/src/NHibernate.Test/NHSpecificTest/GH3134/B.cs
@@ -0,0 +1,12 @@
+using System;
+using System.Collections.Generic;
+
+namespace NHibernate.Test.NHSpecificTest.GH3134
+{
+	public class B
+	{
+		public virtual Guid Id { get; set; }
+		public virtual string NameB { get; set; }
+		public virtual ISet<A> As { get; set; } = new HashSet<A>();
+	}
+}
diff --git a/src/NHibernate.Test/NHSpecificTest/GH3134/BMap.cs b/src/NHibernate.Test/NHSpecificTest/GH3134/BMap.cs
new file mode 100644
index 00000000000..998d4ffbbb5
--- /dev/null
+++ b/src/NHibernate.Test/NHSpecificTest/GH3134/BMap.cs
@@ -0,0 +1,24 @@
+using NHibernate.Mapping.ByCode;
+using NHibernate.Mapping.ByCode.Conformist;
+
+namespace NHibernate.Test.NHSpecificTest.GH3134
+{
+	public class BMap : ClassMapping<B>
+	{
+		public BMap()
+		{
+			this.Table("B");
+			this.Id(x => x.Id, mapper => { mapper.Column("IDB"); mapper.Generator(Generators.Guid); });
+			Property(x => x.NameB);
+			this.Set(
+				x => x.As,
+				collectionMapping =>
+				{
+					collectionMapping.Table("AB");
+					collectionMapping.Key(k => { k.Column("B"); k.ForeignKey("none"); });
+					collectionMapping.Cascade(Mapping.ByCode.Cascade.All);
+				},
+				map => map.ManyToMany(m => { m.Column("A"); }));
+		}
+	}
+}
diff --git a/src/NHibernate.Test/NHSpecificTest/GH3134/ManyToManyChildFetchByCodeFixture.cs b/src/NHibernate.Test/NHSpecificTest/GH3134/ManyToManyChildFetchByCodeFixture.cs
new file mode 100644
index 00000000000..78f359da012
--- /dev/null
+++ b/src/NHibernate.Test/NHSpecificTest/GH3134/ManyToManyChildFetchByCodeFixture.cs
@@ -0,0 +1,79 @@
+using System.Collections.Generic;
+using System.Linq;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Mapping.ByCode;
+using NHibernate.Transform;
+using NHibernate.Util;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH3134
+{
+	[TestFixture]
+	public class ManyToManyChildFetchByCodeFixture : TestCaseMappingByCode
+	{
+		protected override HbmMapping GetMappings()
+		{
+			var mapper = new ModelMapper();
+			mapper.AddMapping<AMap>();
+			mapper.AddMapping<BMap>();
+
+			return mapper.CompileMappingForAllExplicitlyAddedEntities();
+		}
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var a1 = new A();
+				a1.Bs.Add(new B());
+				a1.Bs.Add(new B());
+				session.Save(a1);
+
+				var a2 = new A();
+				a2.Bs.Add(new B());
+				a2.Bs.Add(new B());
+				session.Save(a2);
+
+				transaction.Commit();
+			}
+		}
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.Delete("from System.Object");
+
+				transaction.Commit();
+			}
+		}
+
+		[Test]
+		public void ChildFetchQueryOver()
+		{
+			using (var session = OpenSession())
+			{
+				session.QueryOver<B>().Future();
+
+				session.QueryOver<B>()
+					.Fetch(SelectMode.ChildFetch, b => b)
+					.Fetch(SelectMode.Fetch, b => b.As)
+					.Future();
+
+				var result = session.QueryOver<B>()
+					.Fetch(SelectMode.ChildFetch, b => b, b => b.As)
+					.Fetch(SelectMode.Fetch, b => b.As.First().Bs)
+					.TransformUsing(Transformers.DistinctRootEntity)
+					.Future()
+					.GetEnumerable()
+					.ToList();
+
+				Assert.That(result.Count, Is.EqualTo(4));
+				Assert.That(NHibernateUtil.IsInitialized(result[0].As), Is.True);
+				Assert.That(NHibernateUtil.IsInitialized(result[0].As.First().Bs), Is.True);
+				Assert.That(result[0].As.Count, Is.EqualTo(1));
+				Assert.That(result[0].As.First().Bs.Count, Is.EqualTo(2));
+			}
+		}
+	}
+}
diff --git a/src/NHibernate/Loader/OuterJoinableAssociation.cs b/src/NHibernate/Loader/OuterJoinableAssociation.cs
index 4f50cbfaf3c..c15615bcfe6 100644
--- a/src/NHibernate/Loader/OuterJoinableAssociation.cs
+++ b/src/NHibernate/Loader/OuterJoinableAssociation.cs
@@ -242,6 +242,9 @@ internal string GetSelectFragment(string entitySuffix, string collectionSuffix,
 							                    IncludeLazyProps = SelectMode == SelectMode.FetchLazyProperties,
 						                    });
 				case SelectMode.ChildFetch:
+					// Skip ChildFetch for many-to-many as element id is added by element persister.
+					if (Joinable.IsCollection && ((IQueryableCollection) Joinable).IsManyToMany)
+						return string.Empty;
 					return ReflectHelper.CastOrThrow<ISupportSelectModeJoinable>(Joinable, "child fetch select mode")
 					                    .IdentifierSelectFragment(RHSAlias, entitySuffix);