diff --git a/pkgs/development/python-modules/radon/default.nix b/pkgs/development/python-modules/radon/default.nix
index 007368986c82..6a9baf65e6a6 100644
--- a/pkgs/development/python-modules/radon/default.nix
+++ b/pkgs/development/python-modules/radon/default.nix
@@ -45,6 +45,10 @@ buildPythonPackage rec {
     colorama
   ];
 
+  pythonRelaxDeps = [
+    "mando"
+  ];
+
   optional-dependencies = {
     toml = [ tomli ];
   };