diff --git a/Orm/Xtensive.Orm/Orm/Attributes/IndexAttribute.cs b/Orm/Xtensive.Orm/Orm/Attributes/IndexAttribute.cs
index c5fe78df5f..363f3bd25e 100644
--- a/Orm/Xtensive.Orm/Orm/Attributes/IndexAttribute.cs
+++ b/Orm/Xtensive.Orm/Orm/Attributes/IndexAttribute.cs
@@ -17,7 +17,7 @@ namespace Xtensive.Orm
   /// </example>
   [Serializable]
   [AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface, AllowMultiple = true, Inherited = false)]
-  public sealed class IndexAttribute : StorageAttribute
+  public class IndexAttribute : StorageAttribute
   {
     internal double? fillFactor;
     internal bool? unique;
diff --git a/Version.props b/Version.props
index bc80ec252a..f7ab63251d 100644
--- a/Version.props
+++ b/Version.props
@@ -2,7 +2,7 @@
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
 
 <PropertyGroup>
-    <DoVersion>7.3.19</DoVersion>
+    <DoVersion>7.3.20</DoVersion>
     <DoVersionSuffix>servicetitan</DoVersionSuffix>
 </PropertyGroup>