diff --git a/Makefile b/Makefile
index b54ec93cc..266ad6d20 100644
--- a/Makefile
+++ b/Makefile
@@ -32,7 +32,7 @@ ubuntu.img:
 	unxz ubuntu.img.xz
 
 product_key.txt:
-	echo -ne "X\c" > product_key.txt
+	/usr/bin/echo -ne "X\c" > product_key.txt
 	cat /dev/random | base32 | head -c11 | tr '[:upper:]' '[:lower:]' >> product_key.txt
 	echo >> product_key.txt