diff --git a/pkgs/development/python-modules/setuptools-rust/pyo3-test/default.nix b/pkgs/development/python-modules/setuptools-rust/pyo3-test/default.nix
index 9af17aa5159..31730d6ff2d 100644
--- a/pkgs/development/python-modules/setuptools-rust/pyo3-test/default.nix
+++ b/pkgs/development/python-modules/setuptools-rust/pyo3-test/default.nix
@@ -17,5 +17,9 @@ callPackage ../../../tools/rust/maturin/pyo3-test/generic.nix {
     rust.rustc
   ]);
 
-  sourceRoot = "source/examples/word-count";
+  preConfigure = ''
+    # sourceRoot puts Cargo.lock in the wrong place due to the
+    # example setup.
+    cd examples/word-count
+  '';
 }
diff --git a/pkgs/development/tools/rust/maturin/pyo3-test/generic.nix b/pkgs/development/tools/rust/maturin/pyo3-test/generic.nix
index f82c988fc51..84ca2ddf77f 100644
--- a/pkgs/development/tools/rust/maturin/pyo3-test/generic.nix
+++ b/pkgs/development/tools/rust/maturin/pyo3-test/generic.nix
@@ -10,7 +10,7 @@
 
 , buildAndTestSubdir ? null
 , format ? "pyproject"
-, sourceRoot ? "source"
+, preConfigure ? ""
 }:
 
 python3Packages.buildPythonPackage rec {
@@ -25,14 +25,14 @@ python3Packages.buildPythonPackage rec {
   };
 
   cargoDeps = rustPlatform.fetchCargoTarball {
-    inherit src sourceRoot patches;
+    inherit src patches;
     name = "${pname}-${version}";
     hash = "sha256-//TmozgWy9zrSpMKX92XdHj4fw/T1Elfgn4YhhR7ot0=";
   };
 
   patches = [ ./Cargo.lock.patch ];
 
-  inherit buildAndTestSubdir format nativeBuildInputs sourceRoot;
+  inherit buildAndTestSubdir format nativeBuildInputs preConfigure;
 
   pythonImportsCheck = [ "word_count" ];