diff --git a/boot/zephyr/flash_map_extended.c b/boot/zephyr/flash_map_extended.c
index c77f96c..ffa4500 100644
--- a/boot/zephyr/flash_map_extended.c
+++ b/boot/zephyr/flash_map_extended.c
@@ -27,9 +27,9 @@
 #error "FLASH_DEVICE_ID could not be determined"
 #endif
 
-static struct device *flash_dev;
+static const struct device *flash_dev;
 
-struct device *flash_device_get_binding(char *dev_name)
+const struct device *flash_device_get_binding(char *dev_name)
 {
     if (!flash_dev) {
         flash_dev = device_get_binding(dev_name);
diff --git a/boot/zephyr/include/flash_map_backend/flash_map_backend.h b/boot/zephyr/include/flash_map_backend/flash_map_backend.h
index 20dd379..8b5fd0c 100644
--- a/boot/zephyr/include/flash_map_backend/flash_map_backend.h
+++ b/boot/zephyr/include/flash_map_backend/flash_map_backend.h
@@ -38,7 +38,7 @@
  *
  * Returns the flash device on success, or NULL on failure.
  */
-struct device *flash_device_get_binding(char *dev_name);
+const struct device *flash_device_get_binding(char *dev_name);
 
 /*
  * Retrieve a memory-mapped flash device's base address.