diff --git a/libfprint/fpi-spi-transfer.h b/libfprint/fpi-spi-transfer.h
index 755b405f..0b75673b 100644
--- a/libfprint/fpi-spi-transfer.h
+++ b/libfprint/fpi-spi-transfer.h
@@ -73,6 +73,9 @@ struct _FpiSpiTransfer
   /* Data free function */
   GDestroyNotify free_buffer_wr;
   GDestroyNotify free_buffer_rd;
+
+  /* padding for future expansion */
+  gpointer _padding_dummy[32];
 };
 
 GType              fpi_spi_transfer_get_type (void) G_GNUC_CONST;