diff --git a/lib/stm32/f2/gpio.c b/lib/stm32/f2/gpio.c
index 984cddb1..c577c3ab 100644
--- a/lib/stm32/f2/gpio.c
+++ b/lib/stm32/f2/gpio.c
@@ -86,7 +86,7 @@ void gpio_set_af(u32 gpioport, u8 alt_func_num, u16 gpios)
 	for (i = 8; i < 16; i++) {
 		if (!((1 << i) & gpios))
 			continue;
-		afrl &= ~GPIO_AFR_MASK(i - 8);
+		afrh &= ~GPIO_AFR_MASK(i - 8);
 		afrh |= GPIO_AFR(i - 8, alt_func_num);
 	}
 
diff --git a/lib/stm32/f4/gpio.c b/lib/stm32/f4/gpio.c
index 1d7739dd..aa2fda42 100644
--- a/lib/stm32/f4/gpio.c
+++ b/lib/stm32/f4/gpio.c
@@ -86,7 +86,7 @@ void gpio_set_af(u32 gpioport, u8 alt_func_num, u16 gpios)
 	for (i = 8; i < 16; i++) {
 		if (!((1 << i) & gpios))
 			continue;
-		afrl &= ~GPIO_AFR_MASK(i - 8);
+		afrh &= ~GPIO_AFR_MASK(i - 8);
 		afrh |= GPIO_AFR(i - 8, alt_func_num);
 	}