diff --git a/resources/sql/autopatches/20141106.uniqdrafts.php b/resources/sql/autopatches/20141106.uniqdrafts.php
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20141106.uniqdrafts.php
@@ -0,0 +1,30 @@
+<?php
+
+// Destroy duplicate drafts before storage adjustment adds a unique key to this
+// table. See T1191. We retain the newest draft.
+
+// (We can't easily do this in a single SQL statement because MySQL won't let us
+// modify a table that's joined in a subquery.)
+
+$table = new DifferentialDraft();
+$conn_w = $table->establishConnection('w');
+
+$duplicates = queryfx_all(
+  $conn_w,
+  'SELECT DISTINCT u.id id FROM %T u
+    JOIN %T v
+      ON u.objectPHID = v.objectPHID
+      AND u.authorPHID = v.authorPHID
+      AND u.draftKey = v.draftKey
+      AND u.id < v.id',
+  $table->getTableName(),
+  $table->getTableName());
+
+$duplicates = ipull($duplicates, 'id');
+foreach (PhabricatorLiskDAO::chunkSQL($duplicates) as $chunk) {
+  queryfx(
+    $conn_w,
+    'DELETE FROM %T WHERE id IN (%Q)',
+    $table->getTableName(),
+    $chunk);
+}