diff --git a/Makefile b/Makefile
index 493e132..a235271 100644
--- a/Makefile
+++ b/Makefile
@@ -101,7 +101,7 @@ install-deps:
 	dnf install -y lorax xorriso skopeo
 
 test-iso:
-	_TESTS = $(filter-out README.md,$(shell ls tests/iso))
+	$(eval _TESTS = $(filter-out README.md,$(shell ls tests/iso)))
 	$(foreach test,$(_TESTS),chmod +x tests/iso/$(test))
 	$(foreach test,$(_TESTS),./tests/iso/$(test) deploy.iso)