diff --git a/src/class/usbtmc/usbtmc_device.c b/src/class/usbtmc/usbtmc_device.c
index 59d9b184e..f80abdaf3 100644
--- a/src/class/usbtmc/usbtmc_device.c
+++ b/src/class/usbtmc/usbtmc_device.c
@@ -256,7 +256,7 @@ bool tud_usbtmc_transmit_notification_data(const void * data, size_t len)
   TU_VERIFY(usbd_edpt_busy(usbtmc_state.rhport, usbtmc_state.ep_int_in));
 
   TU_VERIFY(tu_memcpy_s(usbtmc_state.ep_int_in_buf, sizeof(usbtmc_state.ep_int_in_buf), data, len) == 0);
-  TU_VERIFY(usbd_edpt_xfer(usbtmc_state.rhport, usbtmc_state.ep_int_in, usbtmc_state.ep_int_in_buf, len));
+  TU_VERIFY(usbd_edpt_xfer(usbtmc_state.rhport, usbtmc_state.ep_int_in, usbtmc_state.ep_int_in_buf, (uint16_t)len));
   return true;
 }