diff --git a/pkgs/development/interpreters/python/default.nix b/pkgs/development/interpreters/python/default.nix
index ef358c7b63fc..bb709694dc61 100644
--- a/pkgs/development/interpreters/python/default.nix
+++ b/pkgs/development/interpreters/python/default.nix
@@ -36,8 +36,12 @@
             stdenv
           ];
           providesSetupHook = lib.attrByPath [ "provides" "setupHook"] false;
-          valid = value: !lib.isDerivation value || pythonPackages.hasPythonModule value || providesSetupHook value || lib.elem value exceptions;
-          func = name: value: if (valid value) then value else throw "${name} should use `buildPythonPackage` or `toPythonModule` if it is to be part of the Python packages set.";
+          valid = value: pythonPackages.hasPythonModule value || providesSetupHook value || lib.elem value exceptions;
+          func = name: value:
+            if lib.isDerivation value then
+              lib.extendDerivation (valid value || throw "${name} should use `buildPythonPackage` or `toPythonModule` if it is to be part of the Python packages set.") {} value
+            else
+              value;
         in lib.mapAttrs func items;
       in ensurePythonModules (callPackage
         # Function that when called