diff --git a/Makefile b/Makefile
index ac2c08a..4393a33 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
 iso:
-	sudo mkalpineiso -o $PWD/out
+	sudo mkalpineiso -o ${PWD}/out
 
 clean:
 	sudo rm -f ${PWD}/out/*.iso