diff --git a/python/__init__.py b/python/__init__.py
index f5ef5731..9d4722d5 100644
--- a/python/__init__.py
+++ b/python/__init__.py
@@ -525,13 +525,15 @@ class Panda:
     return True
 
   @staticmethod
-  def wait_for_dfu(dfu_serial: str, timeout: Optional[int] = None) -> bool:
+  def wait_for_dfu(dfu_serial: Optional[str], timeout: Optional[int] = None) -> bool:
     t_start = time.monotonic()
-    while dfu_serial not in PandaDFU.list():
+    dfu_list = PandaDFU.list()
+    while (dfu_serial is None and len(dfu_list) == 0) or (dfu_serial is not None and dfu_serial not in dfu_list):
       logging.debug("waiting for DFU...")
       time.sleep(0.1)
       if timeout is not None and (time.monotonic() - t_start) > timeout:
         return False
+      dfu_list = PandaDFU.list()
     return True
 
   def up_to_date(self) -> bool: