--- a/sat/memory/disco.py	Fri Mar 01 17:42:28 2019 +0100
+++ b/sat/memory/disco.py	Fri Mar 01 19:28:11 2019 +0100
@@ -356,6 +356,7 @@
 
         """
         s = []
+        # identities
         byte_identities = [
             ByteIdentity(service)
             for service in services
@@ -367,6 +368,7 @@
         for identity in byte_identities:
             s.append(str(identity))
             s.append("<")
+        # features
         byte_features = [
             service.encode("utf-8")
             for service in services
@@ -376,9 +378,26 @@
         for feature in byte_features:
             s.append(feature)
             s.append("<")
-        # TODO: manage XEP-0128 data form here
+
+        # extensions
+        ext = services.extensions.values()
+        ext.sort(key=lambda f: f.formNamespace.encode('utf-8'))
+        for extension in ext:
+            s.append(extension.formNamespace.encode('utf-8'))
+            s.append("<")
+            fields = extension.fieldList
+            fields.sort(key=lambda f: f.var.encode('utf-8'))
+            for field in fields:
+                s.append(field.var.encode('utf-8'))
+                s.append("<")
+                values = [v.encode('utf-8') for v in field.values]
+                values.sort()
+                for value in values:
+                    s.append(value)
+                    s.append("<")
+
         cap_hash = b64encode(sha1("".join(s)).digest())
-        log.debug(_(u"Capability hash generated: [%s]") % cap_hash)
+        log.debug(_(u"Capability hash generated: [{cap_hash}]").format(cap_hash=cap_hash))
         return cap_hash
 
     @defer.inlineCallbacks