diff --git a/pkgs/servers/mail/mailman/hyperkitty.nix b/pkgs/servers/mail/mailman/hyperkitty.nix
index c55104345989..924accbecfa2 100644
--- a/pkgs/servers/mail/mailman/hyperkitty.nix
+++ b/pkgs/servers/mail/mailman/hyperkitty.nix
@@ -66,7 +66,7 @@ buildPythonPackage rec {
     elasticsearch
     mock
     whoosh
-  ];
+  ] ++ beautifulsoup4.optional-dependencies.lxml;
 
   checkPhase = ''
     cd $NIX_BUILD_TOP/$sourceRoot