diff --git a/pkgs/by-name/fr/fromager/package.nix b/pkgs/by-name/fr/fromager/package.nix
index 914b2d968520..2d3077cca4cf 100644
--- a/pkgs/by-name/fr/fromager/package.nix
+++ b/pkgs/by-name/fr/fromager/package.nix
@@ -59,6 +59,11 @@ python3Packages.buildPythonApplication (finalAttrs: {
   # backoff retries: https://github.com/python-wheel-build/fromager/pull/1348
   env.FROMAGER_HTTP_RETRIES = 0;
 
+  # Tests share repository directories and race during setup:
+  # https://github.com/python-wheel-build/fromager/pull/1349
+  dontUsePytestXdist = true;
+  pytestFlags = [ "--numprocesses=0" ];
+
   pythonImportsCheck = [
     "fromager"
   ];