diff --git a/src/class/usbtmc/usbtmc_device.c b/src/class/usbtmc/usbtmc_device.c
index 0f6d3f60..122b3f3c 100644
--- a/src/class/usbtmc/usbtmc_device.c
+++ b/src/class/usbtmc/usbtmc_device.c
@@ -364,7 +364,7 @@ bool tud_usbtmc_start_bus_read()
   default:
     TU_VERIFY(false);
   }
-  TU_VERIFY(usbd_edpt_xfer(usbtmc_state.rhport, usbtmc_state.ep_bulk_out, usbtmc_state.ep_bulk_out_buf, 64));
+  TU_VERIFY(usbd_edpt_xfer(usbtmc_state.rhport, usbtmc_state.ep_bulk_out, usbtmc_state.ep_bulk_out_buf, (uint16_t)usbtmc_state.ep_bulk_out_wMaxPacketSize));
   return true;
 }