diff --git a/openhtf/plugs/usb/fastboot_device.py b/openhtf/plugs/usb/fastboot_device.py
index 47251bf60..ec53e30cc 100644
--- a/openhtf/plugs/usb/fastboot_device.py
+++ b/openhtf/plugs/usb/fastboot_device.py
@@ -51,6 +51,8 @@ def __init__(self, _, num_retries=3):
   @property
   def usb_handle(self):
     """Return our USB handle."""
+    if not self._protocol:
+      raise usb_exceptions.HandleClosedError()
     return self._protocol.usb_handle
 
   def set_boot_config(self, name, value):