diff --git a/ph-ubl21/src/test/java/com/helger/ubl21/supplementary/issues/Issue63Test.java b/ph-ubl21/src/test/java/com/helger/ubl21/supplementary/issues/Issue63Test.java
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index 00000000..488d0e3a
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+++ b/ph-ubl21/src/test/java/com/helger/ubl21/supplementary/issues/Issue63Test.java
@@ -0,0 +1,147 @@
+/*
+ * Copyright (C) 2014-2024 Philip Helger (www.helger.com)
+ * philip[at]helger[dot]com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.helger.ubl21.supplementary.issues;
+
+import static org.junit.Assert.assertNotNull;
+
+import java.math.BigDecimal;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.w3c.dom.Element;
+
+import com.helger.commons.datetime.PDTFactory;
+import com.helger.ubl21.UBL21Marshaller;
+import com.helger.ubl21.UBL21Marshaller.UBL21JAXBMarshaller;
+
+import oasis.names.specification.ubl.schema.xsd.commonaggregatecomponents_21.CustomerPartyType;
+import oasis.names.specification.ubl.schema.xsd.commonaggregatecomponents_21.InvoiceLineType;
+import oasis.names.specification.ubl.schema.xsd.commonaggregatecomponents_21.ItemType;
+import oasis.names.specification.ubl.schema.xsd.commonaggregatecomponents_21.MonetaryTotalType;
+import oasis.names.specification.ubl.schema.xsd.commonaggregatecomponents_21.SupplierPartyType;
+import oasis.names.specification.ubl.schema.xsd.commonaggregatecomponents_21.TaxCategoryType;
+import oasis.names.specification.ubl.schema.xsd.commonaggregatecomponents_21.TaxSchemeType;
+import oasis.names.specification.ubl.schema.xsd.commonaggregatecomponents_21.TaxSubtotalType;
+import oasis.names.specification.ubl.schema.xsd.commonaggregatecomponents_21.TaxTotalType;
+import oasis.names.specification.ubl.schema.xsd.commonbasiccomponents_21.IDType;
+import oasis.names.specification.ubl.schema.xsd.commonextensioncomponents_21.ExtensionContentType;
+import oasis.names.specification.ubl.schema.xsd.commonextensioncomponents_21.UBLExtensionType;
+import oasis.names.specification.ubl.schema.xsd.commonextensioncomponents_21.UBLExtensionsType;
+import oasis.names.specification.ubl.schema.xsd.commonsignaturecomponents_21.UBLDocumentSignaturesType;
+import oasis.names.specification.ubl.schema.xsd.invoice_21.InvoiceType;
+import oasis.names.specification.ubl.schema.xsd.signatureaggregatecomponents_21.SignatureInformationType;
+
+public final class Issue63Test
+{
+  private static final Logger LOGGER = LoggerFactory.getLogger (Issue63Test.class);
+
+  @Test
+  public void testBasic ()
+  {
+    final String sCurrency = "SAR";
+
+    // Create domain object
+    final InvoiceType aInvoice = new InvoiceType ();
+
+    // Fill it
+    aInvoice.setID ("Dummy Invoice number");
+    aInvoice.setIssueDate (PDTFactory.getCurrentXMLOffsetDateUTC ());
+
+    final SupplierPartyType aSupplier = new SupplierPartyType ();
+    aInvoice.setAccountingSupplierParty (aSupplier);
+
+    final CustomerPartyType aCustomer = new CustomerPartyType ();
+    aInvoice.setAccountingCustomerParty (aCustomer);
+
+    final MonetaryTotalType aMT = new MonetaryTotalType ();
+    aMT.setPayableAmount (BigDecimal.TEN).setCurrencyID (sCurrency);
+    aInvoice.setLegalMonetaryTotal (aMT);
+
+    final InvoiceLineType aLine = new InvoiceLineType ();
+    aLine.setID ("1");
+
+    final ItemType aItem = new ItemType ();
+    aLine.setItem (aItem);
+
+    aLine.setLineExtensionAmount (BigDecimal.TEN).setCurrencyID (sCurrency);
+
+    aInvoice.addInvoiceLine (aLine);
+
+    {
+      final TaxSubtotalType aTaxSubtotal = new TaxSubtotalType ();
+      aTaxSubtotal.setTaxableAmount (BigDecimal.TEN).setCurrencyID (sCurrency);
+      aTaxSubtotal.setTaxAmount (BigDecimal.TEN).setCurrencyID (sCurrency);
+
+      final TaxCategoryType aTaxCategory = new TaxCategoryType ();
+      final IDType aTCID = new IDType ();
+      aTCID.setSchemeID ("UNCL5305");
+      aTCID.setSchemeAgencyID ("6");
+      aTCID.setValue ("Z");
+      aTaxCategory.setID (aTCID);
+
+      aTaxCategory.setPercent (BigDecimal.TEN);
+
+      final TaxSchemeType aTaxScheme = new TaxSchemeType ();
+      final IDType aTSID = new IDType ();
+      aTSID.setSchemeID ("UNCL5305");
+      aTSID.setSchemeAgencyID ("6");
+      aTSID.setValue ("VAT");
+      aTaxScheme.setID (aTSID);
+      aTaxCategory.setTaxScheme (aTaxScheme);
+
+      aTaxSubtotal.setTaxCategory (aTaxCategory);
+
+      final TaxTotalType aTaxTotal = new TaxTotalType ();
+      aTaxTotal.setTaxAmount (BigDecimal.TEN).setCurrencyID (sCurrency);
+      aTaxTotal.addTaxSubtotal (aTaxSubtotal);
+      aInvoice.addTaxTotal (aTaxTotal);
+    }
+
+    // Main extension
+    final UBLExtensionsType ublExtensions = new UBLExtensionsType ();
+    {
+      final UBLExtensionType ublExtension = new UBLExtensionType ();
+      {
+        final ExtensionContentType extensionContent = new ExtensionContentType ();
+        {
+          final UBLDocumentSignaturesType signatures = new UBLDocumentSignaturesType ();
+          final SignatureInformationType signatureInfo = new SignatureInformationType ();
+          signatureInfo.setID ("signatureID");
+          signatures.addSignatureInformation (signatureInfo);
+
+          // Important: convert to Element
+          final Element aSignaturesElement = new UBL21JAXBMarshaller <> (UBLDocumentSignaturesType.class,
+                                                                         UBL21Marshaller.getAllBaseXSDs (),
+                                                                         oasis.names.specification.ubl.schema.xsd.commonsignaturecomponents_21.ObjectFactory._UBLDocumentSignatures_QNAME).getAsElement (signatures);
+
+          extensionContent.setAny (aSignaturesElement);
+          ublExtension.setExtensionURI ("urn:oasis:names:specification:ubl:dsig:enveloped:xades");
+          ublExtension.setExtensionContent (extensionContent);
+        }
+        ublExtensions.addUBLExtension (ublExtension);
+      }
+      aInvoice.setUBLExtensions (ublExtensions);
+    }
+
+    // Write to string
+    final UBL21JAXBMarshaller <InvoiceType> aMarshaller = UBL21Marshaller.invoice ();
+    final String sInvoice = aMarshaller.setFormattedOutput (true).getAsString (aInvoice);
+    assertNotNull (sInvoice);
+    LOGGER.info (sInvoice);
+  }
+}