diff --git a/boot/zephyr/main.c b/boot/zephyr/main.c
index 27fb656..073f4d7 100644
--- a/boot/zephyr/main.c
+++ b/boot/zephyr/main.c
@@ -389,6 +389,9 @@
 
 #if defined(CONFIG_MCUBOOT_SERIAL)
 
+/* The value of -1 is used by default. It must be properly specified for a board before used. */
+BUILD_ASSERT(CONFIG_BOOT_SERIAL_DETECT_PIN != -1);
+
 #define BUTTON_0_GPIO_LABEL CONFIG_BOOT_SERIAL_DETECT_PORT
 #define BUTTON_0_GPIO_PIN CONFIG_BOOT_SERIAL_DETECT_PIN
 #define BUTTON_0_GPIO_FLAGS ((CONFIG_BOOT_SERIAL_DETECT_PIN_VAL) ?\
@@ -397,6 +400,9 @@
 
 #elif defined(CONFIG_BOOT_USB_DFU_GPIO)
 
+/* The value of -1 is used by default. It must be properly specified for a board before used. */
+BUILD_ASSERT(CONFIG_BOOT_USB_DFU_DETECT_PIN != -1);
+
 #define BUTTON_0_GPIO_LABEL CONFIG_BOOT_USB_DFU_DETECT_PORT
 #define BUTTON_0_GPIO_PIN CONFIG_BOOT_USB_DFU_DETECT_PIN
 #define BUTTON_0_GPIO_FLAGS ((CONFIG_BOOT_USB_DFU_DETECT_PIN_VAL) ?\