diff --git a/ports/stm32/usbdev/class/src/usbd_msc_scsi.c b/ports/stm32/usbdev/class/src/usbd_msc_scsi.c
index 50cd5b9715..b5363e2d4b 100644
--- a/ports/stm32/usbdev/class/src/usbd_msc_scsi.c
+++ b/ports/stm32/usbdev/class/src/usbd_msc_scsi.c
@@ -481,7 +481,7 @@ static int8_t SCSI_AllowMediumRemoval(USBD_HandleTypeDef  *pdev, uint8_t lun, ui
 {
   USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   hmsc->bot_data_length = 0;
-  hmsc->bdev_ops->PreventAllowMediumRemoval(lun, params[0]);
+  hmsc->bdev_ops->PreventAllowMediumRemoval(lun, params[4]);
   return 0;
 }