diff --git a/shell.nix b/shell.nix
index f090023..52a99ee 100644
--- a/shell.nix
+++ b/shell.nix
@@ -27,6 +27,7 @@ devshell.mkShell {
       p: with p; [
         python-escpos
         pycups
+        caldav
       ]
     ))
   ];