diff --git a/firmware/drivers/ata_mmc.c b/firmware/drivers/ata_mmc.c
index 897f59b8be..a61d28cb07 100644
--- a/firmware/drivers/ata_mmc.c
+++ b/firmware/drivers/ata_mmc.c
@@ -143,7 +143,7 @@ void mmc_select_clock(int card_no)
 {
     /* set clock gate for external card / reset for internal card if the
      * MMC clock polarity bit is 0, vice versa if it is 1 */
-    if ((card_no != 0) ^ (read_hw_mask() & MMC_CLOCK_POLARITY))
+    if ((card_no != 0) ^ ((read_hw_mask() & MMC_CLOCK_POLARITY) != 0))
         or_b(0x10, &PADRH);       /* set clock gate PA12 */
     else
         and_b(~0x10, &PADRH);     /* clear clock gate PA12 */