diff --git a/boot/zephyr/main.c b/boot/zephyr/main.c
index e5a1eb8..cdd4139 100644
--- a/boot/zephyr/main.c
+++ b/boot/zephyr/main.c
@@ -32,14 +32,14 @@
 
 void os_heap_init(void);
 
+extern void zephyr_flash_area_warn_on_open(void);
+
 #if defined(CONFIG_ARM)
 struct arm_vector_table {
     uint32_t msp;
     uint32_t reset;
 };
 
-extern void zephyr_flash_area_warn_on_open(void);
-
 static void do_boot(struct boot_rsp *rsp)
 {
     struct arm_vector_table *vt;