diff --git a/rules.module b/rules.module
index 80e8161..07d4cac 100644
--- a/rules.module
+++ b/rules.module
@@ -479,7 +479,10 @@ function rules_is_event_configured($event_name, $reset = FALSE) {
     $query->condition('rules_config.active', 1);
     $configured_events = $query->execute()
       ->fetchCol();
-    $rules_event_whitelist = array_combine($configured_events, $configured_events);
+    $rules_event_whitelist = array();
+    if (!empty($configured_events)) {
+      $rules_event_whitelist = array_combine($configured_events, $configured_events);
+    }
     rules_set_cache('rules_event_whitelist', $rules_event_whitelist);
   }
   return isset($rules_event_whitelist[$event_name]);