diff --git a/releasenotes.txt b/releasenotes.txt
index 2f999a17b66..e08c3b4eb23 100644
--- a/releasenotes.txt
+++ b/releasenotes.txt
@@ -311,6 +311,22 @@ Release notes - NHibernate - Version 5.4.0
    * #2242 Test case for NH-3972 - SQL error when selecting a column of a subclass when sibling classes have a column of the same name
 
 
+Build 5.3.20
+=============================
+
+Release notes - NHibernate - Version 5.3.20
+
+2 issues were resolved in this release.
+
+** Bug
+
+   * #3438 DB2/400: ArgumentException Column 'SQL_TYPE_NAME' does not belong to table DataTypes
+
+** Task
+
+   * #3454 Release 5.3.20
+
+
 Build 5.3.19
 =============================
 
diff --git a/src/NHibernate/Dialect/DB2400Dialect.cs b/src/NHibernate/Dialect/DB2400Dialect.cs
index aa306a0d05a..91a23b1a219 100644
--- a/src/NHibernate/Dialect/DB2400Dialect.cs
+++ b/src/NHibernate/Dialect/DB2400Dialect.cs
@@ -1,4 +1,6 @@
-using NHibernate.Cfg;
+using System;
+using System.Data.Common;
+using NHibernate.Dialect.Schema;
 using NHibernate.SqlCommand;
 
 namespace NHibernate.Dialect
@@ -23,7 +25,13 @@ public class DB2400Dialect : DB2Dialect
 	{
 		public DB2400Dialect()
 		{
-			DefaultProperties[Environment.ConnectionDriver] = "NHibernate.Driver.DB2400Driver";
+			DefaultProperties[Cfg.Environment.ConnectionDriver] = "NHibernate.Driver.DB2400Driver";
+		}
+
+		public override IDataBaseSchema GetDataBaseSchema(DbConnection connection)
+		{
+			// The DB2 implementation is not valid for DB2400.
+			throw new NotSupportedException();
 		}
 
 		public override bool SupportsSequences
@@ -61,4 +69,4 @@ public override bool SupportsVariableLimit
 			get { return false; }
 		}
 	}
-}
\ No newline at end of file
+}