diff -r c5850f8f3f5e -r 698ed1c96cd0 mk
--- a/mk	Thu Dec 11 21:13:48 2014 +0000
+++ b/mk	Thu Apr 09 07:42:23 2015 +0100
@@ -1,4 +1,5 @@
 #!/bin/sh
+set -e
 
 subdirs="slides handouts hws coursework"