diff --git a/lib/default.nix b/lib/default.nix
index ab76d69a..0950e9c0 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -38,6 +38,7 @@ rec {
     p.shake
     p.hledger-lib
     p.releaser
+    p.megaparsec
   ]);
   haskellList = list: ''["${builtins.concatStringsSep ''", "'' list}"]'';
   writeHaskellScript =