diff --git a/lib/secretariat/line_item.rb b/lib/secretariat/line_item.rb
index 8f7a683..e10cfce 100644
--- a/lib/secretariat/line_item.rb
+++ b/lib/secretariat/line_item.rb
@@ -154,8 +154,11 @@ def to_xml(xml, line_item_index, version: 2, validate: true)
         if (version == 2)
           xml['ram'].SpecifiedTradeProduct do
             xml['ram'].Name name
-            xml['ram'].OriginTradeCountry do
-              xml['ram'].ID origin_country_code
+            # BT-159 is optional; it describes where goods were made, which a service doesn't have.
+            unless origin_country_code.to_s.empty?
+              xml['ram'].OriginTradeCountry do
+                xml['ram'].ID origin_country_code
+              end
             end
           end
         end
diff --git a/test/invoice_test.rb b/test/invoice_test.rb
index 8af2c76..7148ce8 100644
--- a/test/invoice_test.rb
+++ b/test/invoice_test.rb
@@ -861,6 +861,20 @@ def test_fr_invoice
       assert_match(%r{<ram:SpecifiedLegalOrganization>\s*<ram:ID schemeID="0002">304755032</ram:ID>\s*</ram:SpecifiedLegalOrganization>}, xml)
     end
 
+    def test_origin_country_is_written_when_given
+      xml = make_de_invoice.to_xml(version: 2)
+      assert_match(%r{<ram:OriginTradeCountry>\s*<ram:ID>DE</ram:ID>\s*</ram:OriginTradeCountry>}, xml)
+    end
+
+    def test_line_without_origin_country
+      invoice = make_eu_invoice
+      invoice.line_items.each { |line_item| line_item.origin_country_code = nil }
+      xml = invoice.to_xml(version: 2)
+
+      refute_match(/OriginTradeCountry/, xml)
+      assert_equal [], Validator.new(xml, version: 2).validate_against_schematron
+    end
+
     def test_invoice_with_quantity_causing_sub_cent_amounts
       errors = []