diff --git a/samples/zephyr/Makefile b/samples/zephyr/Makefile
index 464cf6e..ec14c46 100644
--- a/samples/zephyr/Makefile
+++ b/samples/zephyr/Makefile
@@ -257,7 +257,7 @@
 # reset: hello1 runs
 test-no-bootcheck: clean
 	$(MAKE) \
-		BOOTLOADER_CONFIG="-DCONF_VALIDATE_SLOT0=NO" \
+		BOOTLOADER_OVERLAY_CONFIG=$(PWD)/overlay-skip-slot0-validate.conf \
 		SIGNING_KEY=../../root-ec-p256.pem \
 		all
 
diff --git a/samples/zephyr/overlay-skip-slot0-validate.conf b/samples/zephyr/overlay-skip-slot0-validate.conf
new file mode 100644
index 0000000..dd3b2c2
--- /dev/null
+++ b/samples/zephyr/overlay-skip-slot0-validate.conf
@@ -0,0 +1,3 @@
+# Kconfig overlay for building without validating slot 0.
+
+# CONFIG_BOOT_VALIDATE_SLOT0 is not set