diff --git a/tests/subsys/dfu/mcuboot/src/main.c b/tests/subsys/dfu/mcuboot/src/main.c
index 1375549006..245efd46b7 100644
--- a/tests/subsys/dfu/mcuboot/src/main.c
+++ b/tests/subsys/dfu/mcuboot/src/main.c
@@ -95,10 +95,13 @@ void test_write_confirm(void)
 {
 	const uint32_t img_magic[4] = BOOT_MAGIC_VALUES;
 	uint32_t readout[ARRAY_SIZE(img_magic)];
-	const uint32_t flag = 0xffffff01;
+	uint8_t flag[BOOT_MAX_ALIGN];
 	const struct flash_area *fa;
 	int ret;
 
+	flag[0] = 0x01;
+	memset(&flag[1], 0xff, sizeof(flag) - 1);
+
 	ret = flash_area_open(FLASH_AREA_ID(image_0), &fa);
 	if (ret) {
 		printf("Flash driver was not found!\n");