diff --git a/conf/Makefile b/conf/Makefile
index 25c9b80..0fd2e1f 100644
--- a/conf/Makefile
+++ b/conf/Makefile
@@ -23,7 +23,7 @@ clean:
 	rm -f procmailrc muttrc
 
 check: $(FILES) $(XFILES)
-	for i in $(FILES) $(XFILES); do diff ~/.$$i $$i; done
+	for i in $(FILES) $(XFILES); do diff -u ~/.$$i $$i; done
 
 procmailrc muttrc: maildirs.m4
 muttrc: gpg.rc