diff --git a/build.sh b/build.sh
index 11d85bf..3a07414 100755
--- a/build.sh
+++ b/build.sh
@@ -1,7 +1,10 @@
 #!/bin/sh
 
+set -e
+set -x
+
 hugo $(cat .hugo-params)
 ./tools/merge_cals.py
 upcoming="$(tools/gen_upcoming.py static/all.ics 20 5 | tr '\n' ' ')"
 cp static/all.ics public/all.ics
-sed -i "s#CALENDAR#$upcoming#g" public/index.html
\ No newline at end of file
+sed -i "s#CALENDAR#$upcoming#g" public/index.html
diff --git a/flake.nix b/flake.nix
index a52b5ad..73e94d9 100644
--- a/flake.nix
+++ b/flake.nix
@@ -30,6 +30,7 @@
                 python-pkgs.icalendar
                 python-pkgs.pytz
               ]))
+              shellcheck
             ];
           };
         }