diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c
index 391a20b3d2fd..8eb2644506dd 100644
--- a/drivers/spi/spi-stm32.c
+++ b/drivers/spi/spi-stm32.c
@@ -299,9 +299,9 @@ static u32 stm32_spi_prepare_fthlv(struct stm32_spi *spi)
 
 	/* align packet size with data registers access */
 	if (spi->cur_bpw > 8)
-		fthlv -= (fthlv % 2); /* multiple of 2 */
+		fthlv += (fthlv % 2) ? 1 : 0;
 	else
-		fthlv -= (fthlv % 4); /* multiple of 4 */
+		fthlv += (fthlv % 4) ? (4 - (fthlv % 4)) : 0;
 
 	return fthlv;
 }