diff --git a/src/infrastructure/cluster/config/PhabricatorClusterSearchConfigOptionType.php b/src/infrastructure/cluster/config/PhabricatorClusterSearchConfigOptionType.php
--- a/src/infrastructure/cluster/config/PhabricatorClusterSearchConfigOptionType.php
+++ b/src/infrastructure/cluster/config/PhabricatorClusterSearchConfigOptionType.php
@@ -4,7 +4,7 @@
   extends PhabricatorConfigJSONOptionType {
 
   public function validateOption(PhabricatorConfigOption $option, $value) {
-    self::validateClusterSearchConfigValue($value);
+    self::validateValue($value);
   }
 
   public static function validateValue($value) {
diff --git a/src/infrastructure/cluster/search/PhabricatorSearchService.php b/src/infrastructure/cluster/search/PhabricatorSearchService.php
--- a/src/infrastructure/cluster/search/PhabricatorSearchService.php
+++ b/src/infrastructure/cluster/search/PhabricatorSearchService.php
@@ -186,6 +186,18 @@
     $refs = array();
 
     foreach ($services as $config) {
+
+      // Normally, we've validated configuration before we get this far, but
+      // make sure we don't fatal if we end up here with a bogus configuration.
+      if (!isset($engines[$config['type']])) {
+        throw new Exception(
+          pht(
+            'Configured search engine type "%s" is unknown. Valid engines '.
+            'are: %s.',
+            $config['type'],
+            implode(', ', array_keys($engines))));
+      }
+
       $engine = $engines[$config['type']];
       $cluster = new self($engine);
       $cluster->setConfig($config);