diff --git a/session_api.module b/session_api.module
index 0878cd3..778cdae 100644
--- a/session_api.module
+++ b/session_api.module
@@ -100,7 +100,7 @@ function session_api_cron() {
   }
   if (!empty($outdated_sids)) {
     module_invoke_all('session_api_cleanup', $outdated_sids);
-    db_query('DELETE FROM {session_api} WHERE sid IN (' . implode(',', $outdated_sids) . ')');
+    db_query('DELETE FROM {session_api} WHERE sid IN (' . db_placeholders($outdated_sids, 'varchar') . ')');
   }
 }