diff --git a/resources/sql/autopatches/20200428.inline.01.differential.column.sql b/resources/sql/autopatches/20200428.inline.01.differential.column.sql
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20200428.inline.01.differential.column.sql
@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_differential.differential_transaction_comment
+  ADD attributes LONGTEXT NOT NULL COLLATE {$COLLATE_TEXT};
diff --git a/resources/sql/autopatches/20200428.inline.02.diffusion.column.sql b/resources/sql/autopatches/20200428.inline.02.diffusion.column.sql
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20200428.inline.02.diffusion.column.sql
@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_audit.audit_transaction_comment
+  ADD attributes LONGTEXT NOT NULL COLLATE {$COLLATE_TEXT};
diff --git a/resources/sql/autopatches/20200428.inline.03.differential.value.sql b/resources/sql/autopatches/20200428.inline.03.differential.value.sql
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20200428.inline.03.differential.value.sql
@@ -0,0 +1,2 @@
+UPDATE {$NAMESPACE}_differential.differential_transaction_comment
+  SET attributes = '{}' WHERE attributes = '';
diff --git a/resources/sql/autopatches/20200428.inline.04.diffusion.value.sql b/resources/sql/autopatches/20200428.inline.04.diffusion.value.sql
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20200428.inline.04.diffusion.value.sql
@@ -0,0 +1,2 @@
+UPDATE {$NAMESPACE}_audit.audit_transaction_comment
+  SET attributes = '{}' WHERE attributes = '';
diff --git a/src/applications/audit/storage/PhabricatorAuditTransactionComment.php b/src/applications/audit/storage/PhabricatorAuditTransactionComment.php
--- a/src/applications/audit/storage/PhabricatorAuditTransactionComment.php
+++ b/src/applications/audit/storage/PhabricatorAuditTransactionComment.php
@@ -12,6 +12,7 @@
   protected $hasReplies = 0;
   protected $replyToCommentPHID;
   protected $legacyCommentID;
+  protected $attributes = array();
 
   private $replyToComment = self::ATTACHABLE;
 
@@ -54,6 +55,10 @@
       ),
     ) + $config[self::CONFIG_KEY_SCHEMA];
 
+    $config[self::CONFIG_SERIALIZATION] = array(
+      'attributes' => self::SERIALIZATION_JSON,
+    ) + idx($config, self::CONFIG_SERIALIZATION, array());
+
     return $config;
   }
 
diff --git a/src/applications/differential/storage/DifferentialTransactionComment.php b/src/applications/differential/storage/DifferentialTransactionComment.php
--- a/src/applications/differential/storage/DifferentialTransactionComment.php
+++ b/src/applications/differential/storage/DifferentialTransactionComment.php
@@ -11,6 +11,7 @@
   protected $fixedState;
   protected $hasReplies = 0;
   protected $replyToCommentPHID;
+  protected $attributes = array();
 
   private $replyToComment = self::ATTACHABLE;
   private $isHidden = self::ATTACHABLE;
@@ -32,6 +33,7 @@
 
   protected function getConfiguration() {
     $config = parent::getConfiguration();
+
     $config[self::CONFIG_COLUMN_SCHEMA] = array(
       'revisionPHID' => 'phid?',
       'changesetID' => 'id?',
@@ -42,6 +44,7 @@
       'hasReplies' => 'bool',
       'replyToCommentPHID' => 'phid?',
     ) + $config[self::CONFIG_COLUMN_SCHEMA];
+
     $config[self::CONFIG_KEY_SCHEMA] = array(
       'key_draft' => array(
         'columns' => array('authorPHID', 'transactionPHID'),
@@ -53,6 +56,11 @@
         'columns' => array('revisionPHID'),
       ),
     ) + $config[self::CONFIG_KEY_SCHEMA];
+
+    $config[self::CONFIG_SERIALIZATION] = array(
+      'attributes' => self::SERIALIZATION_JSON,
+    ) + idx($config, self::CONFIG_SERIALIZATION, array());
+
     return $config;
   }