diff --git a/makefile b/makefile
index 8523e04..a9d26f3 100644
--- a/makefile
+++ b/makefile
@@ -49,9 +49,7 @@ mykernel.bin: linker.ld $(objects)
 	ld $(LDPARAMS) -T $< -o $@ $(objects)
 
 mykernel.iso: mykernel.bin
-	mkdir iso
-	mkdir iso/boot
-	mkdir iso/boot/grub
+	mkdir -p iso/boot/grub
 	cp mykernel.bin iso/boot/mykernel.bin
 	echo 'set timeout=0'                      > iso/boot/grub/grub.cfg
 	echo 'set default=0'                     >> iso/boot/grub/grub.cfg