diff --git a/Makefile b/Makefile
index 488aefe..d9db864 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,7 @@
 all: 1o 2o 3o ../submission.zip
 
 submission.zip:
+	rm submission.zip
 	git gc
 	zip $@ .git *.py -r