diff --git a/src/NHibernate.Test/Async/NHSpecificTest/GH2627/Fixture.cs b/src/NHibernate.Test/Async/NHSpecificTest/GH2627/Fixture.cs
new file mode 100644
index 00000000000..ac24f9f72c5
--- /dev/null
+++ b/src/NHibernate.Test/Async/NHSpecificTest/GH2627/Fixture.cs
@@ -0,0 +1,69 @@
+//------------------------------------------------------------------------------
+// <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 NUnit.Framework;
+using NHibernate.Linq;
+
+namespace NHibernate.Test.NHSpecificTest.GH2627
+{
+	using System.Threading.Tasks;
+	[TestFixture]
+	public class FixtureAsync : BugTestCase
+	{
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var e1 = new Entity {Name = "Bob"};
+				session.Save(e1);
+
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from Child").ExecuteUpdate();
+				session.CreateQuery("delete from System.Object").ExecuteUpdate();
+
+				transaction.Commit();
+			}
+		}
+
+		[Test]
+		public async Task NullRefInMergeAsync()
+		{
+			Child child;
+			using (var session = OpenSession())
+			using (var t = session.BeginTransaction())
+			{
+				child = new Child
+				{
+					Parent = await (session.Query<Entity>().FirstOrDefaultAsync()),
+					Name = "John"
+				};
+
+				await (t.CommitAsync());
+			}
+
+			using (var session = OpenSession())
+			using (var t = session.BeginTransaction())
+			{
+				await (session.MergeAsync(child));
+				await (t.CommitAsync());
+			}
+		}
+	}
+}
diff --git a/src/NHibernate.Test/NHSpecificTest/GH2627/Child.cs b/src/NHibernate.Test/NHSpecificTest/GH2627/Child.cs
new file mode 100644
index 00000000000..55ac0288207
--- /dev/null
+++ b/src/NHibernate.Test/NHSpecificTest/GH2627/Child.cs
@@ -0,0 +1,11 @@
+using System;
+
+namespace NHibernate.Test.NHSpecificTest.GH2627
+{
+	public class Child
+	{
+		public virtual Guid Id { get; set; }
+		public virtual Entity Parent { get; set; }
+		public virtual string Name { get; set; }
+	}
+}
diff --git a/src/NHibernate.Test/NHSpecificTest/GH2627/Entity.cs b/src/NHibernate.Test/NHSpecificTest/GH2627/Entity.cs
new file mode 100644
index 00000000000..8757939fdf4
--- /dev/null
+++ b/src/NHibernate.Test/NHSpecificTest/GH2627/Entity.cs
@@ -0,0 +1,10 @@
+using System;
+
+namespace NHibernate.Test.NHSpecificTest.GH2627
+{
+	public class Entity
+	{
+		public virtual Guid Id { get; set; }
+		public virtual string Name { get; set; }
+	}
+}
diff --git a/src/NHibernate.Test/NHSpecificTest/GH2627/Fixture.cs b/src/NHibernate.Test/NHSpecificTest/GH2627/Fixture.cs
new file mode 100644
index 00000000000..44f36d3a503
--- /dev/null
+++ b/src/NHibernate.Test/NHSpecificTest/GH2627/Fixture.cs
@@ -0,0 +1,57 @@
+using System.Linq;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH2627
+{
+	[TestFixture]
+	public class Fixture : BugTestCase
+	{
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var e1 = new Entity {Name = "Bob"};
+				session.Save(e1);
+
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from Child").ExecuteUpdate();
+				session.CreateQuery("delete from System.Object").ExecuteUpdate();
+
+				transaction.Commit();
+			}
+		}
+
+		[Test]
+		public void NullRefInMerge()
+		{
+			Child child;
+			using (var session = OpenSession())
+			using (var t = session.BeginTransaction())
+			{
+				child = new Child
+				{
+					Parent = session.Query<Entity>().FirstOrDefault(),
+					Name = "John"
+				};
+
+				t.Commit();
+			}
+
+			using (var session = OpenSession())
+			using (var t = session.BeginTransaction())
+			{
+				session.Merge(child);
+				t.Commit();
+			}
+		}
+	}
+}
diff --git a/src/NHibernate.Test/NHSpecificTest/GH2627/Mappings.hbm.xml b/src/NHibernate.Test/NHSpecificTest/GH2627/Mappings.hbm.xml
new file mode 100644
index 00000000000..6c4296a93e9
--- /dev/null
+++ b/src/NHibernate.Test/NHSpecificTest/GH2627/Mappings.hbm.xml
@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="NHibernate.Test"
+                   namespace="NHibernate.Test.NHSpecificTest.GH2627">
+
+  <class name="Entity">
+    <id name="Id" generator="guid.comb"/>
+    <property name="Name"/>
+  </class>
+
+  <class name="Child">
+    <id name="Id" generator="guid.comb"/>
+    <property name="Name"/>
+    <many-to-one name="Parent" not-found="ignore"/>
+  </class>
+
+</hibernate-mapping>
diff --git a/src/NHibernate/Async/Type/ManyToOneType.cs b/src/NHibernate/Async/Type/ManyToOneType.cs
index e288555bddb..d5615a85d7a 100644
--- a/src/NHibernate/Async/Type/ManyToOneType.cs
+++ b/src/NHibernate/Async/Type/ManyToOneType.cs
@@ -11,7 +11,7 @@
 using System;
 using System.Data.Common;
 using NHibernate.Engine;
-using NHibernate.Persister.Entity;
+using NHibernate.Proxy;
 using NHibernate.SqlTypes;
 using NHibernate.Util;
 
diff --git a/src/NHibernate/Type/ManyToOneType.cs b/src/NHibernate/Type/ManyToOneType.cs
index b38fb35eba8..172bc8f1b99 100644
--- a/src/NHibernate/Type/ManyToOneType.cs
+++ b/src/NHibernate/Type/ManyToOneType.cs
@@ -1,7 +1,7 @@
 using System;
 using System.Data.Common;
 using NHibernate.Engine;
-using NHibernate.Persister.Entity;
+using NHibernate.Proxy;
 using NHibernate.SqlTypes;
 using NHibernate.Util;
 
@@ -162,14 +162,24 @@ private bool IsIdentifier(object value, ISessionImplementor session)
 
 		public override bool IsNull(object owner, ISessionImplementor session)
 		{
-			if (IsNullable && !string.IsNullOrEmpty(PropertyName))
-			{
-				EntityEntry entry = session.PersistenceContext.GetEntry(owner);
+			if (!IsNullable || string.IsNullOrEmpty(PropertyName) || owner == null)
+				return false;
 
-				return session.PersistenceContext.IsPropertyNull(entry.EntityKey, PropertyName);
-			}
+			var entityKey = GetEntityKey(owner, session);
+			if (entityKey == null)
+				return false;
 
-			return false;
+			return session.PersistenceContext.IsPropertyNull(entityKey, PropertyName);
+		}
+
+		private static EntityKey GetEntityKey(object owner, ISessionImplementor session)
+		{
+			var entry = session.PersistenceContext.GetEntry(owner);
+			if (entry != null)
+				return entry.EntityKey;
+			if (owner is INHibernateProxy proxy)
+				return session.GenerateEntityKey(proxy.HibernateLazyInitializer.Identifier, session.Factory.GetEntityPersister(proxy.HibernateLazyInitializer.EntityName));
+			return null;
 		}
 
 		public override object Disassemble(object value, ISessionImplementor session, object owner)