diff --git a/src/bridge/DBus.py b/src/bridge/DBus.py
index d53531a4..5bbffdf8 100755
--- a/src/bridge/DBus.py
+++ b/src/bridge/DBus.py
@@ -42,6 +42,9 @@ class InternalError(dbus.DBusException):
 class AsyncNotDeferred(dbus.DBusException):
     _dbus_error_name = const_ERROR_PREFIX + ".AsyncNotDeferred"
 
+class DeferredNotAsync(dbus.DBusException):
+    _dbus_error_name = const_ERROR_PREFIX + ".DeferredNotAsync"
+
 class GenericException(dbus.DBusException):
     def __init__(self, twisted_error):
         super(GenericException,self).__init__()
@@ -82,6 +85,9 @@ class DbusObject(dbus.service.Object):
             result.addCallback(callback)
             result.addErrback(lambda err:errback(GenericException(err)))
         else:
+            if isinstance(result, Deferred):
+                error("Synchrone method [%s] return a Deferred." % name)
+                raise DeferredNotAsync
             return result
 
     ### signals ###    
diff --git a/src/bridge/bridge_constructor/dbus_core_template.py b/src/bridge/bridge_constructor/dbus_core_template.py
index 9097d672..da5c6942 100644
--- a/src/bridge/bridge_constructor/dbus_core_template.py
+++ b/src/bridge/bridge_constructor/dbus_core_template.py
@@ -42,6 +42,9 @@ class InternalError(dbus.DBusException):
 class AsyncNotDeferred(dbus.DBusException):
     _dbus_error_name = const_ERROR_PREFIX + ".AsyncNotDeferred"
 
+class DeferredNotAsync(dbus.DBusException):
+    _dbus_error_name = const_ERROR_PREFIX + ".DeferredNotAsync"
+
 class GenericException(dbus.DBusException):
     def __init__(self, twisted_error):
         super(GenericException,self).__init__()
@@ -82,6 +85,9 @@ class DbusObject(dbus.service.Object):
             result.addCallback(callback)
             result.addErrback(lambda err:errback(GenericException(err)))
         else:
+            if isinstance(result, Deferred):
+                error("Synchrone method [%s] return a Deferred." % name)
+                raise DeferredNotAsync
             return result
 
     ### signals ###