diff --git a/tools/kete.py b/tools/kete.py
index 8f20ea2..17d0fc2 100755
--- a/tools/kete.py
+++ b/tools/kete.py
@@ -271,7 +271,7 @@ class TuhiKeteDevice(_DBusObject):
         self.live = False
 
     def json(self, timestamp):
-        return self.proxy.GetJSONData('(u)', timestamp)
+        return self.proxy.GetJSONData('(t)', timestamp)
 
     def _on_signal_received(self, proxy, sender, signal, parameters):
         if signal == 'ButtonPressRequired':
diff --git a/tuhi/dbusserver.py b/tuhi/dbusserver.py
index 4582dec..afd6e4e 100755
--- a/tuhi/dbusserver.py
+++ b/tuhi/dbusserver.py
@@ -87,7 +87,7 @@ INTROSPECTION_XML = '''
     </method>
 
     <method name='GetJSONData'>
-      <arg name='index' type='u' direction='in'/>
+      <arg name='timestamp' type='t' direction='in'/>
       <arg name='json' type='s' direction='out'/>
     </method>