diff --git a/pkgs/development/python-modules/mandown/default.nix b/pkgs/development/python-modules/mandown/default.nix
index eae43bc8d951..37231a55afc2 100644
--- a/pkgs/development/python-modules/mandown/default.nix
+++ b/pkgs/development/python-modules/mandown/default.nix
@@ -34,6 +34,7 @@ buildPythonPackage rec {
   ];
 
   pythonRelaxDeps = [
+    "lxml"
     "pillow"
     "typer"
   ];