diff --git a/plugins/libkolab/lib/kolab_storage_cache.php b/plugins/libkolab/lib/kolab_storage_cache.php
index 8e4e19c4..9a16799e 100644
--- a/plugins/libkolab/lib/kolab_storage_cache.php
+++ b/plugins/libkolab/lib/kolab_storage_cache.php
@@ -494,7 +494,7 @@ class kolab_storage_cache
     protected function _sql_where($query)
     {
         $sql_where = '';
-        foreach ($query as $param) {
+        foreach ((array) $query as $param) {
             if (is_array($param[0])) {
                 $subq = array();
                 foreach ($param[0] as $q) {