diff --git a/resources/sql/autopatches/20180306.opath.03.purge.php b/resources/sql/autopatches/20180306.opath.03.purge.php
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20180306.opath.03.purge.php
@@ -0,0 +1,22 @@
+<?php
+
+$table = new PhabricatorOwnersPath();
+$conn = $table->establishConnection('w');
+
+$seen = array();
+foreach (new LiskMigrationIterator($table) as $path) {
+  $package_id = $path->getPackageID();
+  $repository_phid = $path->getRepositoryPHID();
+  $path_index = $path->getPathIndex();
+
+  if (!isset($seen[$package_id][$repository_phid][$path_index])) {
+    $seen[$package_id][$repository_phid][$path_index] = true;
+    continue;
+  }
+
+  queryfx(
+    $conn,
+    'DELETE FROM %T WHERE id = %d',
+    $table->getTableName(),
+    $path->getID());
+}
diff --git a/resources/sql/autopatches/20180306.opath.04.unique.sql b/resources/sql/autopatches/20180306.opath.04.unique.sql
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20180306.opath.04.unique.sql
@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_owners.owners_path
+  ADD UNIQUE KEY `key_path` (packageID, repositoryPHID, pathIndex);
diff --git a/src/applications/owners/storage/PhabricatorOwnersPath.php b/src/applications/owners/storage/PhabricatorOwnersPath.php
--- a/src/applications/owners/storage/PhabricatorOwnersPath.php
+++ b/src/applications/owners/storage/PhabricatorOwnersPath.php
@@ -20,8 +20,9 @@
         'excluded' => 'bool',
       ),
       self::CONFIG_KEY_SCHEMA => array(
-        'packageID' => array(
-          'columns' => array('packageID'),
+        'key_path' => array(
+          'columns' => array('packageID', 'repositoryPHID', 'pathIndex'),
+          'unique' => true,
         ),
       ),
     ) + parent::getConfiguration();