diff --git a/src/applications/search/engineextension/PhabricatorFulltextIndexEngineExtension.php b/src/applications/search/engineextension/PhabricatorFulltextIndexEngineExtension.php
index 0767849abe..ab4da88420 100644
--- a/src/applications/search/engineextension/PhabricatorFulltextIndexEngineExtension.php
+++ b/src/applications/search/engineextension/PhabricatorFulltextIndexEngineExtension.php
@@ -1,92 +1,116 @@
 <?php
 
 final class PhabricatorFulltextIndexEngineExtension
   extends PhabricatorIndexEngineExtension {
 
   const EXTENSIONKEY = 'fulltext';
 
+  private $configurationVersion;
+
   public function getExtensionName() {
     return pht('Fulltext Engine');
   }
 
   public function getIndexVersion($object) {
     $version = array();
 
+    // When "cluster.search" is reconfigured, new indexes which don't have any
+    // data yet may have been added. We err on the side of caution and assume
+    // that every document may need to be reindexed.
+    $version[] = $this->getConfigurationVersion();
+
     if ($object instanceof PhabricatorApplicationTransactionInterface) {
       // If this is a normal object with transactions, we only need to
       // reindex it if there are new transactions (or comment edits).
       $version[] = $this->getTransactionVersion($object);
       $version[] = $this->getCommentVersion($object);
     }
 
     if (!$version) {
       return null;
     }
 
     return implode(':', $version);
   }
 
   public function shouldIndexObject($object) {
     return ($object instanceof PhabricatorFulltextInterface);
   }
 
   public function indexObject(
     PhabricatorIndexEngine $engine,
     $object) {
 
     $engine = $object->newFulltextEngine();
     if (!$engine) {
       return;
     }
 
     $engine->setObject($object);
 
     $engine->buildFulltextIndexes();
   }
 
   private function getTransactionVersion($object) {
     $xaction = $object->getApplicationTransactionTemplate();
 
     $xaction_row = queryfx_one(
       $xaction->establishConnection('r'),
       'SELECT id FROM %T WHERE objectPHID = %s
         ORDER BY id DESC LIMIT 1',
       $xaction->getTableName(),
       $object->getPHID());
     if (!$xaction_row) {
       return 'none';
     }
 
     return $xaction_row['id'];
   }
 
   private function getCommentVersion($object) {
     $xaction = $object->getApplicationTransactionTemplate();
 
     try {
       $comment = $xaction->getApplicationTransactionCommentObject();
       if (!$comment) {
         return 'none';
       }
     } catch (Exception $ex) {
       return 'none';
     }
 
     $comment_row = queryfx_one(
       $comment->establishConnection('r'),
       'SELECT c.id FROM %T x JOIN %T c
         ON x.phid = c.transactionPHID
         WHERE x.objectPHID = %s
         ORDER BY c.id DESC LIMIT 1',
       $xaction->getTableName(),
       $comment->getTableName(),
       $object->getPHID());
     if (!$comment_row) {
       return 'none';
     }
 
     return $comment_row['id'];
   }
 
+  private function getConfigurationVersion() {
+    if ($this->configurationVersion === null) {
+      $this->configurationVersion = $this->newConfigurationVersion();
+    }
+    return $this->configurationVersion;
+  }
+
+  private function newConfigurationVersion() {
+    $raw = array(
+      'services' => PhabricatorEnv::getEnvConfig('cluster.search'),
+    );
+
+    $json = phutil_json_encode($raw);
+
+    return PhabricatorHash::digestForIndex($json);
+  }
+
 
 }