diff --git a/chip/stm32l/gpio.c b/chip/stm32l/gpio.c
index 0f3e7f44a5..d56efa32d4 100644
--- a/chip/stm32l/gpio.c
+++ b/chip/stm32l/gpio.c
@@ -29,15 +29,17 @@ int gpio_pre_init(void)
 	 */
 	STM32L_RCC_AHBENR |= 0x3f;
 
-	/* Set all GPIOs to defaults */
 	for (i = 0; i < GPIO_COUNT; i++, g++) {
 		/* bitmask for registers with 2 bits per GPIO pin */
 		uint32_t mask2 = (g->mask * g->mask) | (g->mask * g->mask * 2);
+		uint32_t val;
 
+		val = STM32L_GPIO_PUPDR_OFF(g->port) & ~mask2;
 		if (g->flags & GPIO_PULL_UP) /* Pull Up = 01 */
-			STM32L_GPIO_PUPDR_OFF(g->port) |= 0x55555555 & mask2;
+			val |= 0x55555555 & mask2;
 		else if (g->flags & GPIO_PULL_DOWN) /* Pull Down = 10 */
-			STM32L_GPIO_PUPDR_OFF(g->port) |= 0xaaaaaaaa & mask2;
+			val |= 0xaaaaaaaa & mask2;
+		STM32L_GPIO_PUPDR_OFF(g->port) = val;
 
 		if (g->flags & GPIO_OPEN_DRAIN)
 			STM32L_GPIO_OTYPER_OFF(g->port) |= g->mask;
@@ -47,11 +49,13 @@ int gpio_pre_init(void)
 		 * potential damage, e.g. driving an open-drain output
 		 * high before it has been configured as such.
 		 */
+		val = STM32L_GPIO_MODER_OFF(g->port) & ~mask2;
 		if (g->flags & GPIO_OUTPUT) { /* General purpose, MODE = 01 */
-			STM32L_GPIO_MODER_OFF(g->port) |= 0x55555555 & mask2;
+			val |= 0x55555555 & mask2;
+			STM32L_GPIO_MODER_OFF(g->port) = val;
 			gpio_set_level(i, g->flags & GPIO_HIGH);
-		} else if (g->flags & GPIO_INPUT) {
-			STM32L_GPIO_MODER_OFF(g->port) &= ~mask2;
+		} else if (g->flags & GPIO_INPUT) { /* Input, MODE=00 */
+			STM32L_GPIO_MODER_OFF(g->port) = val;
 		}
 
 		/* Set up interrupts if necessary */