diff --git a/yunohost_tools.py b/yunohost_tools.py
index 9c956184..b8f18056 100644
--- a/yunohost_tools.py
+++ b/yunohost_tools.py
@@ -230,6 +230,16 @@ def tools_postinstall(domain, password, dyndns=False):
         password -- YunoHost admin password
 
     """
+    if len(domain.split('.')) >= 3:
+        r = requests.get('http://dyndns.yunohost.org/domains')
+        dyndomains = json.loads(r.text)
+        dyndomain  = '.'.join(new_domain.split('.')[1:])
+        if dyndomain in dyndomains:
+            if requests.get('http://dyndns.yunohost.org/test/'+ domain).status_code == 200:
+                dyndns=True
+            else:
+                raise YunoHostError(17, _("Domain is already taken"))
+
     with YunoHostLDAP(password='yunohost') as yldap:
         try:
             with open('/etc/yunohost/installed') as f: pass