diff --git a/dvg_appointments.client.inc b/dvg_appointments.client.inc
index 4f2a63a..98e9fcf 100644
--- a/dvg_appointments.client.inc
+++ b/dvg_appointments.client.inc
@@ -18,6 +18,10 @@ abstract class AppointmentsClientApi {
 
       ksort($args);
       $cid = 'dvg_appointments__' . $function . '__' . substr(md5(serialize($args)), 0, 8);
+      if (module_exists('domain')) {
+        $current_domain = domain_get_domain();
+        $cid .= ':' . $current_domain['machine_name'];
+      }
       $cache = cache_get($cid);
       if (!$reset && $cache) {