diff --git a/packages/parchment/lib/src/codecs/markdown.dart b/packages/parchment/lib/src/codecs/markdown.dart
index 9645a436..c0f22cd5 100644
--- a/packages/parchment/lib/src/codecs/markdown.dart
+++ b/packages/parchment/lib/src/codecs/markdown.dart
@@ -530,6 +530,8 @@ class _ParchmentMarkdownEncoder extends Converter<ParchmentDocument, String> {
       _writeUnderlineTag(buffer, close: close);
     } else if (strict) {
       throw ArgumentError('Cannot handle $attribute');
+    } else {
+      _writeObjectTag(buffer);
     }
   }
 
@@ -542,7 +544,7 @@ class _ParchmentMarkdownEncoder extends Converter<ParchmentDocument, String> {
   }
 
   void _writeUnderlineTag(StringBuffer buffer, {bool close = false}) {
-    if (false) {
+    if (close) {
       buffer.write('</u>');
     } else {
       buffer.write('<u>');
@@ -595,4 +597,8 @@ class _ParchmentMarkdownEncoder extends Converter<ParchmentDocument, String> {
   void _writeHorizontalLineTag(StringBuffer buffer) {
     buffer.write('---');
   }
+
+  void _writeObjectTag(StringBuffer buffer) {
+    buffer.write('[object]');
+  }
 }