diff --git a/pkgs/development/python-modules/cython/0.nix b/pkgs/development/python-modules/cython/0.nix
index a54ebfa8b156..53d0847d1d90 100644
--- a/pkgs/development/python-modules/cython/0.nix
+++ b/pkgs/development/python-modules/cython/0.nix
@@ -58,7 +58,7 @@ buildPythonPackage rec {
     ncurses
   ];
 
-  LC_ALL = "en_US.UTF-8";
+  env.LC_ALL = "en_US.UTF-8";
 
   patches = [
     # backport Cython 3.0 trashcan support (https://github.com/cython/cython/pull/2842) to 0.X series.