diff --git a/tinygrad/runtime/support/usb.py b/tinygrad/runtime/support/usb.py
index 920d798aba..5e64b207ba 100644
--- a/tinygrad/runtime/support/usb.py
+++ b/tinygrad/runtime/support/usb.py
@@ -1,7 +1,7 @@
 import ctypes, struct, dataclasses, array, itertools
 from typing import Sequence
 from tinygrad.runtime.autogen import libusb
-from tinygrad.helpers import DEBUG
+from tinygrad.helpers import DEBUG, to_mv
 from tinygrad.runtime.support.hcq import MMIOInterface
 
 class USB3:
@@ -46,6 +46,7 @@ class USB3:
     self.buf_stat = [(ctypes.c_uint8 * 64)() for _ in range(self.max_streams)]
     self.buf_data_in = [(ctypes.c_uint8 * 0x1000)() for _ in range(self.max_streams)]
     self.buf_data_out = [(ctypes.c_uint8 * 0x1000)() for _ in range(self.max_streams)]
+    self.buf_data_out_mvs = [to_mv(ctypes.addressof(self.buf_data_out[i]), 0x1000) for i in range(self.max_streams)]
 
   def _prep_transfer(self, tr, ep, stream_id, buf, length):
     tr.contents.dev_handle, tr.contents.endpoint, tr.contents.length, tr.contents.buffer = self.handle, ep, length, buf
@@ -86,8 +87,11 @@ class USB3:
         tr_window.append(self._prep_transfer(self.tr[self.ep_data_in][slot], self.ep_data_in, stream, self.buf_data_in[slot], rlen))
 
       if send_data is not None:
-        if len(send_data) > len(self.buf_data_out[slot]): self.buf_data_out[slot] = (ctypes.c_uint8 * len(send_data))()
-        self.buf_data_out[slot][:len(send_data)] = list(send_data)
+        if len(send_data) > len(self.buf_data_out[slot]):
+          self.buf_data_out[slot] = (ctypes.c_uint8 * len(send_data))()
+          self.buf_data_out_mvs[slot] = to_mv(ctypes.addressof(self.buf_data_out[slot]), len(send_data))
+
+        self.buf_data_out_mvs[slot][:len(send_data)] = bytes(send_data)
         tr_window.append(self._prep_transfer(self.tr[self.ep_data_out][slot], self.ep_data_out, stream, self.buf_data_out[slot], len(send_data)))
 
       op_window.append((idx, slot, rlen))