diff --git a/board/provision.h b/board/provision.h
index 9091322..0b09d8f 100644
--- a/board/provision.h
+++ b/board/provision.h
@@ -11,3 +11,9 @@ void get_provision_chunk(uint8_t *resp) {
   }
 }
 
+uint8_t chunk[PROVISION_CHUNK_LEN];
+bool is_provisioned(void) {
+  (void)memcpy(chunk, (uint8_t *)0x1fff79e0, PROVISION_CHUNK_LEN);
+  return (memcmp(chunk, "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff", 0x20) != 0);
+}
+
diff --git a/board/spi_flasher.h b/board/spi_flasher.h
index fbdbab8..b9f38dd 100644
--- a/board/spi_flasher.h
+++ b/board/spi_flasher.h
@@ -68,8 +68,8 @@ int usb_cb_control_msg(USB_Setup_TypeDef *setup, uint8_t *resp, bool hardwired)
           #ifdef ALLOW_DEBUG
           if (hardwired) {
           #else
-          // no more bootstub on UNO
-          if (hardwired && hw_type != HW_TYPE_UNO) {
+          // no more bootstub on UNO once OTP block is flashed
+          if (hardwired && ((hw_type != HW_TYPE_UNO) || (!is_provisioned()))) {
           #endif
             puts("-> entering bootloader\n");
             enter_bootloader_mode = ENTER_BOOTLOADER_MAGIC;