diff --git a/panda/__init__.py b/panda/__init__.py
index 18f9c02e..77ba6c08 100644
--- a/panda/__init__.py
+++ b/panda/__init__.py
@@ -184,7 +184,7 @@ class Panda(object):
           break
         except Exception:
           print("reconnecting is taking %d seconds..." % (i+1))
-          if i == 14:
+          if i == 13:
             try:
               dfu = PandaDFU(PandaDFU.st_serial_to_dfu_serial(self._serial))
               dfu.recover()
diff --git a/panda/dfu.py b/panda/dfu.py
index 079e1e12..782b4dca 100644
--- a/panda/dfu.py
+++ b/panda/dfu.py
@@ -21,7 +21,7 @@ class PandaDFU(object):
           this_dfu_serial = device._getASCIIStringDescriptor(3)
         except Exception:
           continue
-        if this_dfu_serial == dfu_serial:
+        if this_dfu_serial == dfu_serial or dfu_serial is None:
           self._handle = device.open()
           self.legacy = "07*128Kg" in self._handle.getASCIIStringDescriptor(4)
           return
@@ -44,6 +44,8 @@ class PandaDFU(object):
 
   @staticmethod
   def st_serial_to_dfu_serial(st):
+    if st == None or st == "none":
+      return None
     uid_base = struct.unpack("H"*6, st.decode("hex"))
     return struct.pack("!HHH", uid_base[1] + uid_base[5], uid_base[0] + uid_base[4] + 0xA, uid_base[3]).encode("hex").upper()