diff --git a/jmbase/jmbase/bigstring.py b/jmbase/jmbase/bigstring.py
index f7135ad..dcc90a1 100644
--- a/jmbase/jmbase/bigstring.py
+++ b/jmbase/jmbase/bigstring.py
@@ -43,7 +43,7 @@ class BigString(amp.Argument):
             nextChunk = value.read(CHUNK_MAX)
             if not nextChunk:
                 break
-            strings["%s.%d" % (name, counter)] = nextChunk
+            strings["{}.{}".format(name, counter).encode('ascii')] = nextChunk
             counter += 1
 
     def fromvalue(self, value):
diff --git a/jmbase/test/test_commands.py b/jmbase/test/test_commands.py
index 7bde889..70dac85 100644
--- a/jmbase/test/test_commands.py
+++ b/jmbase/test/test_commands.py
@@ -66,8 +66,8 @@ class JMTestServerProtocol(JMBaseProtocol):
         return {'accepted': True}
 
     @JMSetup.responder
-    def on_JM_SETUP(self, role, n_counterparties):
-        show_receipt("JMSETUP", role,n_counterparties)
+    def on_JM_SETUP(self, role, initdata):
+        show_receipt("JMSETUP", role, initdata)
         d = self.callRemote(JMSetupDone)
         self.defaultCallbacks(d)
         return {'accepted': True}
@@ -157,7 +157,7 @@ class JMTestClientProtocol(JMBaseProtocol):
         show_receipt("JMUP")
         d = self.callRemote(JMSetup,
                             role="TAKER",
-                            n_counterparties=4) #TODO this number should be set
+                            initdata="none")
         self.defaultCallbacks(d)
         return {'accepted': True}