diff --git a/third_party/default.nix b/third_party/default.nix
index ea03f4736..02df1365c 100644
--- a/third_party/default.nix
+++ b/third_party/default.nix
@@ -77,6 +77,7 @@ let
       graphviz
       gzip
       haskell
+      haskellPackages
       iana-etc
       imagemagickBig
       installShellFiles