diff --git a/simulator/extctrl2014.py b/simulator/extctrl2014.py
index 67af2c59b159d1adbd1e5f921f52ee2468e2eadc..23782c10ee87ed8acc7cff479bb66184cdd3471c 100644
--- a/simulator/extctrl2014.py
+++ b/simulator/extctrl2014.py
@@ -328,6 +328,9 @@ class ExtCtrl(object):
                     if packet.index == self.ack:
                         self.ack = None
                         self.cond.notify_all()
+                    else:
+                        if self.packetdebug:
+                            print "Unexpected ack %x (exp: %x)" % (packet.index, self.ack)
                     if packet.kind == kind_INIT and self.remote_index == None:
                         decoder = Decoder(packet.data)
                         with self.cond: