diff --git a/examples/isotp.py b/examples/isotp.py
index a07703354dcde6..fd300da751c2d5 100644
--- a/examples/isotp.py
+++ b/examples/isotp.py
@@ -9,6 +9,23 @@ def msg(x):
     assert False
   return ret.ljust(8, "\x00")
 
+kmsgs = []
+def recv(panda, cnt, addr, nbus):
+  global kmsgs
+  ret = []
+
+  while len(ret) < cnt:
+    kmsgs += panda.can_recv()
+    nmsgs = []
+    for ids, ts, dat, bus in kmsgs:
+      if ids == addr and bus == nbus and len(ret) < cnt:
+        ret.append(dat)
+      else:
+        # leave around
+        nmsgs.append((ids, ts, dat, bus))
+    kmsgs = nmsgs[-256:]
+  return map(str, ret)
+
 def isotp_send(panda, x, addr, bus=0, recvaddr=None):
   if recvaddr is None:
     recvaddr = addr+8
@@ -30,22 +47,6 @@ def isotp_send(panda, x, addr, bus=0, recvaddr=None):
     rr = recv(panda, 1, recvaddr, bus)[0]
     panda.can_send_many([(addr, None, s, 0) for s in sends])
 
-kmsgs = []
-def recv(panda, cnt, addr, nbus):
-  global kmsgs
-  ret = []
-
-  while len(ret) < cnt:
-    kmsgs += panda.can_recv()
-    nmsgs = []
-    for ids, ts, dat, bus in kmsgs:
-      if ids == addr and bus == nbus and len(ret) < cnt:
-        ret.append(dat)
-      else:
-        pass
-    kmsgs = nmsgs
-  return map(str, ret)
-
 def isotp_recv(panda, addr, bus=0, sendaddr=None):
   msg = recv(panda, 1, addr, bus)[0]