diff --git a/pkgs/development/python-modules/pyerfa/default.nix b/pkgs/development/python-modules/pyerfa/default.nix
index 0f3da6940a6d..5ed9dab2a770 100644
--- a/pkgs/development/python-modules/pyerfa/default.nix
+++ b/pkgs/development/python-modules/pyerfa/default.nix
@@ -38,7 +38,7 @@ buildPythonPackage rec {
   '';
 
   # See https://github.com/liberfa/pyerfa/issues/112#issuecomment-1721197483
-  NIX_CFLAGS_COMPILE = "-O2";
+  env.NIX_CFLAGS_COMPILE = "-O2";
   nativeCheckInputs = [
     pytestCheckHook
     pytest-doctestplus