diff --git a/frontends/src/jp/cmd_debug.py b/frontends/src/jp/cmd_debug.py
index ac737e66..61fa2360 100644
--- a/frontends/src/jp/cmd_debug.py
+++ b/frontends/src/jp/cmd_debug.py
@@ -54,8 +54,9 @@ class Method(base.CommandBase, BridgeCommon):
         self.parser.add_argument("method", type=str, help=_(u"name of the method to execute"))
         self.parser.add_argument("arg", type=base.unicode_decoder, nargs="*", help=_(u"argument of the method"))
 
-    def method_cb(self, ret):
-        self.disp(unicode(ret))
+    def method_cb(self, ret=None):
+        if ret is not None:
+            self.disp(unicode(ret))
         self.host.quit()
 
     def method_eb(self, failure):