diff --git a/src/execo_g5k/api_utils.py b/src/execo_g5k/api_utils.py
index 273d915f40e88e08af4f25a1ac7bf8af757d481d..016fe0bd29b6fd12b70a8d982b115d4ce89abdf4 100644
--- a/src/execo_g5k/api_utils.py
+++ b/src/execo_g5k/api_utils.py
@@ -653,6 +653,8 @@ def get_host_longname(host):
         host_site = mo.group(3)
     else:
         host_site = get_host_site(host_shortname)
+        if not host_site:
+            return None
     return host_shortname + "." + host_site + ".grid5000.fr"
 
 def __get_site_metrics(site, grouped_hosts, metric, from_ts, to_ts, resolution):