diff --git a/pkgs/top-level/python-packages.nix b/pkgs/top-level/python-packages.nix
index eb38aff56ba3..2cd41b23c166 100644
--- a/pkgs/top-level/python-packages.nix
+++ b/pkgs/top-level/python-packages.nix
@@ -25788,7 +25788,7 @@ EOF
     };
   };
 
-  topydo = builtins.trace "python3Packages.topydo was moved to topydo" pkgs.topydo; # 2017-09-22
+  topydo = throw "python3Packages.topydo was moved to topydo"; # 2017-09-22
 
   w3lib = buildPythonPackage rec {
     name = "w3lib-${version}";