diff --git a/drivers/spi/spi-mux.c b/drivers/spi/spi-mux.c
index f4b619cc2657..c02c4204442f 100644
--- a/drivers/spi/spi-mux.c
+++ b/drivers/spi/spi-mux.c
@@ -158,6 +158,7 @@ static int spi_mux_probe(struct spi_device *spi)
 	/* supported modes are the same as our parent's */
 	ctlr->mode_bits = spi->controller->mode_bits;
 	ctlr->flags = spi->controller->flags;
+	ctlr->bits_per_word_mask = spi->controller->bits_per_word_mask;
 	ctlr->transfer_one_message = spi_mux_transfer_one_message;
 	ctlr->setup = spi_mux_setup;
 	ctlr->num_chipselect = mux_control_states(priv->mux);