diff --git a/modules/dream2nix/WIP-python-pdm/default.nix b/modules/dream2nix/WIP-python-pdm/default.nix
index 128c0a8e..ae2c9e6c 100644
--- a/modules/dream2nix/WIP-python-pdm/default.nix
+++ b/modules/dream2nix/WIP-python-pdm/default.nix
@@ -186,14 +186,11 @@ in {
           inherit name;
           version = lib.mkDefault pkg.version;
           sourceSelector = lib.mkOptionDefault config.pdm.sourceSelector;
-          buildPythonPackage =
+          buildPythonPackage.format = lib.mkDefault (
             if lib.hasSuffix ".whl" source.file
-            then {
-              format = lib.mkDefault "wheel";
-            }
-            else {
-              pyproject = lib.mkDefault true;
-            };
+            then "wheel"
+            else null
+          );
           mkDerivation = {
             # TODO: handle sources outside pypi.org
             src = lib.mkDefault (libpyproject-fetchers.fetchFromLegacy {
diff --git a/modules/dream2nix/pip/default.nix b/modules/dream2nix/pip/default.nix
index 4c803f72..ba6f0a5a 100644
--- a/modules/dream2nix/pip/default.nix
+++ b/modules/dream2nix/pip/default.nix
@@ -56,14 +56,12 @@
     # deps.python cannot be defined in commonModule as this would trigger an
     #   infinite recursion.
     deps = {inherit python;};
-    buildPythonPackage =
+    buildPythonPackage.format = lib.mkDefault (
       if lib.hasSuffix ".whl" cfg.mkDerivation.src
-      then {
-        format = lib.mkDefault "wheel";
-      }
-      else {
-        pyproject = lib.mkDefault true;
-      };
+      then "wheel"
+      else null
+    );
+
     mkDerivation.buildInputs =
       lib.optionals
       (! lib.hasSuffix ".whl" cfg.mkDerivation.src)