diff --git a/Makefile b/Makefile
index 7e959f3..c19c6eb 100644
--- a/Makefile
+++ b/Makefile
@@ -2,6 +2,8 @@ all: upstreaming
 
 upstreaming:
 	moban -m mobanfile
+	git diff
+	git diff --ignore-blank-lines | while read line; do if [ "$line" ]; then exit 1; fi; done
 
 lint: flake8 . --exclude=.moban.d,docs --builtins=unicode,xrange,long