diff --git a/pkgs/development/python-modules/tqdm/default.nix b/pkgs/development/python-modules/tqdm/default.nix
index 541a9510dea1..0ca33fd88fe7 100644
--- a/pkgs/development/python-modules/tqdm/default.nix
+++ b/pkgs/development/python-modules/tqdm/default.nix
@@ -50,7 +50,7 @@ buildPythonPackage rec {
   # Too sensitive for on Hydra.
   disabledTests = [ "perf" ];
 
-  LC_ALL = "en_US.UTF-8";
+  env.LC_ALL = "en_US.UTF-8";
 
   pythonImportsCheck = [ "tqdm" ];